Display unit, display module, and electronic device

ABSTRACT

An object is to provide a highly reliable display unit having a function of sensing light. The display unit includes a light-receiving device and a light-emitting device. The light-receiving device includes an active layer between a pair of electrodes. The light-emitting device includes a hole-injection layer, a light-emitting layer, and an electron-transport layer between a pair of electrodes. The light-receiving device and the light-emitting device share one of the electrodes, and may further share another common layer between the pair of electrodes. The hole-injection layer is in contact with an anode and contains a first compound and a second compound. The electron-transport property of the electron-transport layer is low; hence, the light-emitting layer is less likely to have excess electrons. Here, the first compound is the material having a property of accepting electrons from the second compound.

BACKGROUND OF THE INVENTION 1. Field of the Invention

One embodiment of the present invention relates to a display unit, adisplay module, and an electronic device. One embodiment of the presentinvention relates to a display unit including a light-receiving device(also referred to as a light-receiving element) and a light-emittingdevice (also referred to as a light-emitting element).

Note that one embodiment of the present invention is not limited to theabove technical field. Examples of the technical field of one embodimentof the present invention include a semiconductor device, a display unit,a light-emitting unit, a power storage device, a memory device, anelectronic device, a lighting device, an input device (such as a touchsensor), an input/output device (such as a touch panel), a method fordriving any of them, and a method for manufacturing any of them.

2. Description of the Related Art

Recent display units have been expected to be applied to a variety ofuses. Examples of uses for a large display unit include a televisiondevice for home use (also referred to as a TV or a television receiver),digital signage, and a public information display (PID). In addition, asmartphone and a tablet terminal including a touch panel are beingdeveloped as portable information terminals.

Light-emitting units including light-emitting devices have beendeveloped as display units. Light-emitting devices utilizingelectroluminescence (hereinafter referred to as EL; such devices arealso referred to as EL devices or EL elements) have features such asease of reduction in thickness and weight, high-speed response to inputsignals, and driving with low DC voltage, and have been used in displayunits. For example, Patent Document 1 discloses a flexiblelight-emitting unit using an organic EL device (also referred to as anorganic EL element).

REFERENCE

-   [Patent Document 1] Japanese Published Patent Application No.    2014-197522

SUMMARY OF THE INVENTION

An object of one embodiment of the present invention is to provide adisplay unit having a function of sensing light. An object of oneembodiment of the present invention is to provide a highly reliabledisplay unit having a function of sensing light. An object of oneembodiment of the present invention is to provide a highly convenientdisplay unit. An object of one embodiment of the present invention is toprovide a multifunctional display unit. An object of one embodiment ofthe present invention is to provide a display unit with high displayquality. An object of one embodiment of the present invention is toprovide a display unit having highlight sensitivity. An object of oneembodiment of the present invention is to provide a novel display unit.

Note that the description of these objects does not preclude theexistence of other objects. One embodiment of the present invention doesnot need to achieve all these objects. Other objects can be derived fromthe descriptions of the specification, the drawings, and the claims.

One embodiment of the present invention is a display unit including alight-receiving device and a light-emitting device. The light-receivingdevice includes a first pixel electrode, an active layer, and a commonelectrode. The light-emitting device includes a second pixel electrode,a hole-injection layer, a light-emitting layer, an electron-transportlayer, and the common electrode. The active layer is positioned over thefirst pixel electrode and contains a first organic compound. Thelight-emitting layer is positioned over the second pixel electrode andcontains a second organic compound different from the first organiccompound. The common electrode includes a portion overlapping with thefirst pixel electrode with the active layer therebetween, and a portionoverlapping with the second pixel electrode with the light-emittinglayer therebetween. The hole-injection layer is in contact with theanode, which is one of the second pixel electrode and the commonelectrode. The hole-injection layer contains a first compound and asecond compound. The electron-transport layer contains anelectron-transport material. The first compound has a property ofaccepting electrons from the second compound. The second compound has aHOMO level higher than or equal to −5.7 eV and lower than or equal to−5.4 eV. The electron-transport material has a HOMO level higher than orequal to −6.0 eV, and has an electron mobility higher than or equal to1×10⁻⁷ cm²/Vs and lower than or equal to 5×10⁻⁵ cm² when the square rootof electric field strength [V/cm] is 600. The light-receiving devicefurther preferably includes the hole-injection layer. It is preferredthat the hole-injection layer be positioned over the first pixelelectrode and the second pixel electrode, and include a portionoverlapping with the active layer and a portion overlapping with thelight-emitting layer.

One embodiment of the present invention is a display unit including alight-receiving device and a light-emitting device. The light-receivingdevice includes a first pixel electrode, an active layer, and a commonelectrode. The light-emitting device includes a second pixel electrode,a light-emitting layer, an electron-transport layer, and the commonelectrode. The active layer is positioned over the first pixel electrodeand contains a first organic compound. The light-emitting layer ispositioned over the second pixel electrode and contains a second organiccompound different from the first organic compound. The common electrodeincludes a portion overlapping with the first pixel electrode with theactive layer therebetween, and a portion overlapping with the secondpixel electrode with the light-emitting layer therebetween. Theelectron-transport layer contains an electron-transport material and afirst substance. The first substance is a metal, a metallic salt, ametal oxide, or an organometallic complex. The electron-transport layerincludes a first region and a second region. The concentration of thefirst substance in the first region is different from the concentrationof the first substance in the second region. When the first region ispositioned closer to the light-emitting layer than the second region is,the concentration of the first substance is preferably higher than inthe first region than in the second region. It is preferred that theelectron-transport material have a HOMO level higher than or equal to−6.0 eV, and have an electron mobility higher than or equal to 1×10⁻⁷cm²/Vs and lower than or equal to 5×10⁻⁵ cm² when the square root ofelectric field strength [V/cm] is 600. The light-emitting device furtherpreferably includes a hole-injection layer. It is preferred that thehole-injection layer be in contact with the anode, which is one of thesecond pixel electrode and the common electrode, and contain a firstcompound and a second compound. The first compound preferably has aproperty of accepting electrons from the second compound. The secondcompound preferably has a HOMO level higher than or equal to −5.7 eV andlower than or equal to −5.4 eV.

The light-receiving device further preferably includes theelectron-transport layer. It is preferred that the electron-transportlayer be positioned over the first pixel electrode and the second pixelelectrode, and include a portion overlapping with the active layer and aportion overlapping with the light-emitting layer.

The light-receiving device and the light-emitting device preferablyfurther include a common layer. It is preferable that the common layerbe positioned over the first pixel electrode and the second pixelelectrode, and include a portion overlapping with the active layer and aportion overlapping with the light-emitting layer.

The light-emitting device further preferably includes a firsthole-transport layer. The first hole-transport layer preferably containsa third compound. It is preferred that the HOMO level of the thirdcompound be lower than or equal to the HOMO level of the secondcompound, and that the difference in the HOMO level between the thirdcompound and the second compound be 0.2 eV or less. The second compoundand the third compound each preferably include at least one of acarbazole skeleton, a dibenzofuran skeleton, a dibenzothiopheneskeleton, and an anthracene skeleton.

The light-emitting device further preferably includes a secondhole-transport layer. The second hole-transport layer preferablycontains a fourth compound. The HOMO level of the fourth compound ispreferably lower than that of the third compound. The second compound,the third compound, and the fourth compound each preferably include atleast one of a carbazole skeleton, a dibenzofuran skeleton, adibenzothiophene skeleton, and an anthracene skeleton.

The first substance is preferably an organometallic complex containingan alkali metal or an alkaline earth metal. The first substance ispreferably an organometallic complex including a ligand containingnitrogen and oxygen, and an alkali metal or an alkaline earth metal. Thefirst substance is preferably an organometallic complex including aquinolinol ligand, and an alkali metal or an alkaline earth metal.

The light-emitting device preferably emits blue light.

The light-emitting device is preferably a fluorescent device.

The display unit of one embodiment of the present invention preferablyfurther includes a resin layer, a light-blocking layer, and a substrate.The resin layer and the light-blocking layer are preferably positionedbetween the common electrode and the substrate,

For example, the resin layer preferably has an opening overlapping withthe light-receiving device. The resin layer preferably includes aportion overlapping with the light-emitting device. The light-blockinglayer preferably includes a portion between the common electrode and theresin layer. The light-blocking layer preferably covers at least part ofthe opening and at least part of a side surface of the resin layerexposed in the opening.

Alternatively, it is preferable that the resin layer have an islandshape and include a portion overlapping with the light-emitting device.The light-blocking layer preferably include a portion between the commonelectrode and the resin layer. At least part of light passing throughthe substrate enters the light-receiving device without via the resinlayer. The light-blocking layer preferably covers at least part of aside surface of the resin layer.

The display unit of one embodiment of the present invention preferablyfurther includes an adhesive layer. The adhesive layer is preferablypositioned between the common electrode and the substrate. The resinlayer and the light-blocking layer are preferably positioned between theadhesive layer and the substrate. The adhesive layer preferably includesa first portion overlapping with the light-receiving device and a secondportion overlapping with the light-emitting device. The first portion ispreferably thicker than the second portion.

The display unit of one embodiment of the present invention preferablyhas flexibility.

One embodiment of the present invention is a module including thedisplay unit having any of the above structures. For example, the moduleis provided with a connector such as a flexible printed circuit (FPC) ora tape carrier package (TCP) or is mounted with an integrated circuit(IC) by a chip on glass (COG) method, a chip on film (COF) method, orthe like.

One embodiment of the present invention is an electronic deviceincluding the aforementioned module and at least one of an antenna, abattery, a housing, a camera, a speaker, a microphone, and an operationbutton.

One embodiment of the present invention can provide a display unithaving a function of sensing light. One embodiment of the presentinvention can provide a highly reliable display unit having a functionof sensing light. One embodiment of the present invention can provide ahighly convenient display unit. One embodiment of the present inventioncan provide a multifunctional display unit. One embodiment of thepresent invention can provide a display unit with high display quality.One embodiment of the present invention can provide a display unithaving high light sensitivity. One embodiment of the present inventioncan provide a novel display unit.

Note that the description of these effects does not preclude theexistence of other effects. One embodiment of the present invention doesnot need to have all these effects. Other effects can be derived fromthe descriptions of the specification, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIGS. 1A to 1D are cross-sectional views illustrating examples ofdisplay units, and FIGS. 1E to 1I are top views illustrating examples ofpixels;

FIG. 2 is a cross-sectional view illustrating an example of a displayunit;

FIG. 3A is a cross-sectional view illustrating an example of a displayunit, and FIGS. 3B and 3C illustrate examples of a top-view layout of aresin layer;

FIGS. 4A and 4B are cross-sectional views each illustrating an exampleof a display unit;

FIGS. 5A to 5C are cross-sectional views each illustrating an example ofa display unit;

FIGS. 6A to 6C are cross-sectional views each illustrating an example ofa display unit;

FIG. 7A is a top view illustrating an example of a display unit, andFIG. 7B is a cross-sectional view illustrating an example of the displayunit;

FIGS. 8A and 8B are cross-sectional views each illustrating an exampleof a display unit;

FIG. 9A is a top view illustrating an example of a display unit, andFIG. 9B is a cross-sectional view illustrating an example of the displayunit;

FIG. 10A is a top view illustrating an example of a display unit, andFIG. 10B is a cross-sectional view illustrating an example of thedisplay unit;

FIGS. 11A and 11B are cross-sectional views each illustrating an exampleof a display unit;

FIGS. 12A and 12B are cross-sectional views illustrating an example of adisplay unit;

FIG. 13 is a perspective view illustrating an example of a display unit;

FIG. 14 is a cross-sectional view illustrating an example of a displayunit;

FIGS. 15A and 15B are cross-sectional views each illustrating an exampleof a display unit;

FIG. 16 is a cross-sectional view illustrating an example of a displayunit;

FIG. 17A is a cross-sectional view illustrating an example of a displayunit, and FIG. 17B is a cross-sectional view illustrating an example ofa transistor;

FIGS. 18A to 18D are cross-sectional views each illustrating an exampleof a light-emitting device;

FIGS. 19A to 19C are conceptual diagrams illustrating light emissionmodels of light-emitting devices, and FIG. 19D shows normalizedluminance of light-emitting devices over time;

FIGS. 20A to 20D each show the concentration of a first substance in anelectron-transport layer;

FIGS. 21A and 21B are circuit diagrams each illustrating an example of apixel circuit;

FIG. 22A is a block diagram illustrating an example of a pixel, and FIG.22B is a circuit diagram illustrating an example of a pixel circuit;

FIGS. 23A and 23B illustrate an example of an electronic device;

FIGS. 24A to 24D illustrate examples of electronic devices;

FIGS. 25A to 25F illustrate examples of electronic devices;

FIG. 26 illustrates a structure of an electron-only device;

FIG. 27 shows current density-voltage characteristics of anelectron-only device;

FIG. 28 shows frequency characteristics of capacitance C calculated at aDC voltage of 7.0 V when the ratio of ZADN to Liq is 1:1;

FIG. 29 shows frequency characteristics of −ΔB at a DC voltage of 7.0 Vwhen the ratio of ZADN to Liq is 1:1; and

FIG. 30 shows electric field strength dependence of electron mobility oforganic compounds.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments will be described in detail with reference to the drawings.Note that the present invention is not limited to the followingdescription, and it will be readily appreciated by those skilled in theart that modes and details of the present invention can be modified invarious ways without departing from the spirit and scope of the presentinvention. Therefore, the present invention should not be construed asbeing limited to the description in the following embodiments.

Note that in structures of the present invention described below, thesame portions or portions having similar functions are denoted by thesame reference numerals in different drawings, and the descriptionthereof is not repeated. The same hatching pattern is used for portionshaving similar functions, and the portions are not denoted by specificreference numerals in some cases.

The position, size, range, or the like of each component illustrated indrawings does not represent the actual position, size, range, or thelike in some cases for easy understanding. Therefore, the disclosedinvention is not necessarily limited to the position, size, range, orthe like disclosed in the drawings.

Note that the term “film” and the term “layer” can be interchanged witheach other depending on the case or circumstances. For example, the term“conductive layer” can be replaced with the term “conductive film”. Asanother example, the term “insulating film” can be replaced with theterm “insulating layer”.

Embodiment 1

In this embodiment, a display unit of one embodiment of the presentinvention will be described with reference to FIGS. 1A to 1I to FIGS.18A to 18D.

In a display unit of this embodiment, a display portion includeslight-receiving devices and light-emitting devices. In the display unitof this embodiment, the light-emitting devices are arranged in a matrixin the display portion, and an image can be displayed on the displayportion. Moreover, the light-receiving devices are arranged in a matrixin the display portion, so that the display portion also functions as alight-receiving portion. The light-receiving portion can be used as animage sensor or a touch sensor. That is, by sensing light with thelight-receiving portion, an image can be taken and the approach orcontact of an object (e.g., a finger or a stylus) can be detected.Furthermore, in the display unit of this embodiment, the light-emittingdevices can be used as a light source of the sensor. Accordingly, alight-receiving portion and a light source do not need to be providedseparately from the display unit; hence, the number of components of anelectronic device can be reduced.

In the display unit of this embodiment, when an object reflects lightemitted from the light-emitting device included in the display portion,the light-receiving device can sense the reflected light; thus, imagingand touch (including near touch) detection are possible even in a darkplace.

The display unit of this embodiment has a function of displaying imagesusing the light-emitting devices. That is, the light-emitting devicefunctions as a display device.

As the light-emitting device, an EL device such as an organiclight-emitting diode (OLED) and a quantum-dot light-emitting diode(QLED) is preferably used. Examples of a light-emitting substanceincluded in the EL device include a substance exhibiting fluorescence (afluorescent material), a substance exhibiting phosphorescence (aphosphorescent material), an inorganic compound (e.g., a quantum dotmaterial), and a substance exhibiting thermally activated delayedfluorescence (a thermally activated delayed fluorescent (TADF)material). Alternatively, an LED such as a micro-LED can be used as thelight-emitting device.

The display unit of this embodiment has a function of sensing lightusing the light-receiving device.

When the light-receiving device is used as an image sensor, the displayunit of this embodiment can capture an image using the light-receivingdevice. For example, the display unit of this embodiment can be used asa scanner.

For example, data on a fingerprint, a palm print, an iris, or the likecan be acquired with the image sensor. That is, a biologicalauthentication sensor can be incorporated into the display unit of thisembodiment. When the display unit incorporates a biologicalauthentication sensor, the number of components of an electronic devicecan be reduced as compared to the case where a biological authenticationsensor is provided separately from a display unit; thus, the size andweight of the electronic device can be reduced.

In addition, data on facial expression, eye movement, change of thepupil diameter, or the like of the user can be acquired with the imagesensor. By analysis of the data, data on the user's physical and mentalstate can be acquired. Changing the output contents of one or both ofdisplay and sound on the basis of the data allows the user to safely usea device for virtual reality (VR), augmented reality (AR), or mixedreality (MR), for example.

When the light-receiving device is used as the touch sensor, the displayunit of this embodiment can detect the approach or contact of an objectwith the use of the light-receiving device.

As the light-receiving device, a PN photodiode or a PIN photodiode canbe used, for example. The light-receiving device functions as aphotoelectric conversion device that senses light entering thelight-receiving device and generates electric charge. The amount ofgenerated electric charge depends on the amount of incident light.

It is particularly preferable to use an organic photodiode including alayer containing an organic compound as the light-receiving device. Anorganic photodiode, which is easily made thin, lightweight, and large inarea and has a high degree of freedom for shape and design, can be usedin a variety of display units.

In one embodiment of the present invention, an organic EL device is usedas the light-emitting device, and an organic photodiode is used as thelight-receiving device. The organic EL device and the organic photodiodecan be formed over one substrate. Thus, the organic photodiode can beincorporated into the display unit including the organic EL device.

If all the layers of the organic EL device and the organic photodiodeare formed separately, the number of film formation steps becomesextremely large. Since a large number of layers in the organicphotodiode can be common to the layers in the organic EL device, formingthe common layers concurrently can prevent the increase in the number offilm formation steps. Even when the number of film formation steps isthe same, reducing the number of layers formed only in either device cansuppress the influence of deviation of a film formation pattern and theinfluence of dust (including small foreign substances called particles)attached to a deposition mask (e.g., a metal mask), for example. Thus,the yield of the manufacturing process of the display unit can beincreased.

For example, one of a pair of electrodes (a common electrode) can be alayer shared by the light-receiving device and the light-emittingdevice. As another example, at least one of a hole-injection layer, ahole-transport layer, an electron-transport layer, and anelectron-injection layer is preferably a layer shared by thelight-receiving device and the light-emitting device. As anotherexample, an active layer of the light-receiving device and alight-emitting layer of the light-emitting device are separately formed,and the other layers can be shared by the light-emitting device and thelight-receiving device. When the light-receiving device and thelight-emitting device include common layers in such a manner, the numberof film formation steps and the number of masks can be reduced, therebyreducing the number of manufacturing steps and the manufacturing cost ofthe display unit.

Note that a layer shared by the light-receiving device and thelight-emitting device may have a different function depending on whichdevice the layer is in. In this specification, the name of a componentis based on its function in the light-emitting device. For example, ahole-injection layer functions as a hole-injection layer in thelight-emitting device and functions as a hole-transport layer in thelight-receiving device. Similarly, an electron-injection layer functionsas an electron-injection layer in the light-emitting device andfunctions as an electron-transport layer in the light-receiving device.

A display unit of one embodiment of the present invention includes alight-receiving device and a light-emitting device in a display portion.The light-receiving device includes a first pixel electrode, an activelayer, and a common electrode. The light-emitting device includes asecond pixel electrode, a light-emitting layer, and the commonelectrode. The active layer is positioned over the first pixel electrodeand contains a first organic compound. The light-emitting layer ispositioned over the second pixel electrode and contains a second organiccompound different from the first organic compound. The common electrodeincludes a portion overlapping with the first pixel electrode with theactive layer therebetween, and a portion overlapping with the secondpixel electrode with the light-emitting layer therebetween.

The light-emitting device preferably further includes a hole-injectionlayer and an electron-transport layer. In that case, the hole-injectionlayer is in contact with the anode, which is one of the second pixelelectrode and the common electrode. The hole-injection layer contains afirst compound and a second compound. The electron-transport layercontains an electron-transport material. The first compound has aproperty of accepting electrons from the second compound. The secondcompound has a HOMO level higher than or equal to −5.7 eV and lower thanor equal to −5.4 eV. The electron-transport material has a HOMO levelhigher than or equal to −6.0 eV, and has an electron mobility higherthan or equal to 1×10⁻⁷ cm²/Vs and lower than or equal to 5×10⁻⁵ cm²when the square root of electric field strength [V/cm] is 600.

Alternatively, the light-emitting device preferably further includes anelectron-transport layer. In that case, the electron-transport layercontains an electron-transport material and a first substance. The firstsubstance is a metal, a metallic salt, a metal oxide, or anorganometallic complex. The electron-transport layer includes a firstregion and a second region. The concentration of the first substance inthe first region is different from the concentration of the firstsubstance in the second region. For example, when the first region ispositioned closer to the light-emitting layer than the second region is,the concentration of the first substance is preferably higher than inthe first region than in the second region. It is preferred that theelectron-transport material have a HOMO level higher than or equal to−6.0 eV, and have an electron mobility higher than or equal to 1×10⁻⁷cm²/Vs and lower than or equal to 5×10⁻⁵ cm² when the square root ofelectric field strength [V/cm] is 600.

In the light-emitting device of one embodiment of the present invention,holes are likely to be injected into the light-emitting layer andelectrons are less likely to be injected into the light-emitting layer.Holes are easily injected from the anode side and the amount ofelectrons injected into the light-emitting layer from the cathode sideis controlled, whereby the light-emitting layer can be prevented fromhaving excess electrons. Moreover, injection of electrons into thelight-emitting layer over time increases luminance, and the luminanceincrease can cancel out initial decay. Using a light-emitting devicewith little initial decay and an extremely long driving lifetime resultsin high reliability. Note that the light-emitting device used in thedisplay unit of one embodiment of the present invention will bedescribed in detail in Embodiment 2.

In the display unit of one embodiment of the present invention, lightemitted from the light-emitting device is extracted through a displaysurface, and light with which the light-receiving device is irradiatedpasses through the display surface. The display unit preferably includesa light-blocking layer on the display surface side of the light-emittingdevice and the light-receiving device. Light emitted from thelight-emitting device is preferably extracted to the outside of thedisplay unit through an opening in the light-blocking layer (or a regionwhere the light-blocking layer is not provided). The light-receivingdevice is preferably irradiated with light passing through an opening inthe light-blocking layer (or a region where the light-blocking layer isnot provided).

The light-receiving device senses light that is emitted from thelight-emitting device and then reflected by an object. However, in somecases, light emitted from the light-emitting device is reflected insidethe display unit and enters the light-receiving device without via anobject. Such stray light ends up as noise in light detection, which is afactor reducing the signal-to-noise ratio (S/N ratio). Providing thelight-blocking layer on the display surface side of the light-emittingdevice and the light-receiving device can reduce the influence of straylight. Thus, noise can be reduced, and the sensitivity of the sensorusing the light-receiving device can be increased.

As the light-blocking layer is positioned closer to the light-emittingdevice, stray light from the light-emitting device inside the displayunit can be reduced and the sensitivity of the sensor can be increased.Furthermore, as the light-blocking layer is positioned closer to thelight-emitting device, the amount of contrast reduction and chromaticitychange at the time when the display unit is seen from the obliquedirection can be reduced, and viewing angle characteristics of displaycan be more favorable. On the other hand, as the light-blocking layer ispositioned further from the light-emitting device, the area of theimaging range of the light-receiving device can be smaller, and theimaging resolution can be higher.

In view of the above, in one embodiment of the present invention, acomponent (e.g., a resin layer) is provided on a surface where thelight-blocking layer is formed, to cause a difference between thedistance from the light-blocking layer to the light-receiving device andthe distance from the light-blocking layer to the light-emitting device.Adjusting the layout and thickness of the component can increase thedistance from the light-blocking layer to the light-receiving device andreduce the distance from the light-blocking layer to the light-emittingdevice. Accordingly, noise of the sensor can be reduced, the imagingresolution can be increased, and viewing angle dependence of display canbe reduced. Thus, both the display quality and imaging quality of thedisplay unit can be increased.

Specifically, it is preferred that the display unit of one embodiment ofthe present invention include a resin layer, a light-blocking layer, anda substrate. The resin layer and the light-blocking layer are preferablypositioned between the common electrode and the substrate.

At least part of light emitted from the light-emitting device isextracted to the outside of the substrate through the resin layer. Atleast part of light passing through the substrate enters thelight-receiving device without via the resin layer. For example, theresin layer has an opening overlapping with the light-receiving device.Alternatively, the resin layer is provided to have an island shape in aregion overlapping with the light-emitting device.

The resin layer is provided at the position overlapping with thelight-emitting device and is not provided at the position overlappingwith the light-receiving device. Thus, the distance from thelight-blocking layer to the light-emitting device is shorter than thedistance from the light-blocking layer to the light-receiving device.Consequently, both the display quality and imaging quality of thedisplay unit can be increased.

FIGS. 1A to 1D are cross-sectional views of display units of oneembodiment of the present invention.

A display unit 50A illustrated in FIG. TA includes a layer 53 includinglight-receiving devices and a layer 57 including light-emitting devices,between a substrate 51 and a substrate 59.

A display unit 50B illustrated in FIG. 1B includes the layer 53including light-receiving devices, a layer 55 including transistors, andthe layer 57 including light-emitting devices, between the substrate 51and the substrate 59.

In the display unit 50A and the display unit 50B, red (R) light, green(G) light, and blue (B) light are emitted from the layer 57 includinglight-emitting devices.

The display unit of one embodiment of the present invention includes aplurality of pixels arranged in a matrix. One pixel includes at leastone subpixel. One subpixel includes one light-emitting device. Forexample, a pixel can include three subpixels (e.g., three colors of R,G, and B or three colors of yellow (Y), cyan (C), and magenta (M)) orfour subpixels (e.g., four colors of R, G, B, and white (W) or fourcolors of R, G, B, and Y). The pixel also includes alight-receivingdevice. The light-receiving device may be provided in all the pixels orin some of the pixels. In addition, one pixel may include a plurality oflight-receiving devices.

The layer 55 including transistors preferably includes a firsttransistor and a second transistor. The first transistor is electricallyconnected to the light-receiving device. The second transistor iselectrically connected to the light-emitting device.

The display unit of one embodiment of the present invention may have afunction of sensing an object such as a finger that is touching thedisplay unit. For example, after light emitted from the light-emittingdevice in the layer 57 including light-emitting devices is reflected bya finger 52 that touches the display unit 50B as illustrated in FIG. 1C,the light-receiving device in the layer 53 including light-receivingdevices senses the reflected light. Thus, the touch of the finger 52 onthe display unit 50B can be detected.

The display unit of one embodiment of the present invention may have afunction of sensing an object that is approaching (but is not touching)the display unit 50B as illustrated in FIG. 1D or capturing an image ofsuch an object.

[Pixel]

FIGS. 1E to 1I illustrate examples of pixels.

The pixel illustrated in each of FIGS. 1E to 1G includes three subpixels(three light-emitting devices) of R, G, and B and a light-receivingdevice PD. FIG. 1E illustrates an example in which the three subpixelsand the light-receiving device PD are arranged in a 2×2 matrix. FIG. 1Fillustrates an example in which the three subpixels and thelight-receiving device PD are arranged horizontally in one line. FIG. 1Gillustrates an example in which the three subpixels are arrangedhorizontally in one line and the light-receiving device PD is placedbeneath the subpixels. Note that each of the pixels in FIGS. 1E to 1Gcan be said to consist of four subpixels, among which three subpixelsare used to perform display and one subpixel is used to sense light.

The pixel illustrated in FIG. 1H includes four subpixels (fourlight-emitting devices) of R, G, B, and W and the light-receiving devicePD.

The pixel illustrated in FIG. 1I includes three subpixels of R, G, andB, a light-emitting device IR that emits infrared light, and thelight-receiving device PD. Here, the light-receiving device PDpreferably has a function of sensing infrared light. The light-receivingdevice PD may have a function of sensing both visible light and infraredlight. The wavelength of light that the light-receiving device PD sensescan be determined depending on the application of the sensor.

The detailed structures of the light-emitting device and thelight-receiving device included in the display unit of one embodiment ofthe present invention will be described below with reference to FIG. 2to FIGS. 12A and 12B.

The display unit of one embodiment of the present invention can have anyof the following structures: a top-emission structure in which light isemitted in a direction opposite to the substrate where thelight-emitting device is formed, a bottom-emission structure in whichlight is emitted toward the substrate where the light-emitting device isformed, and a dual-emission structure in which light is emitted towardboth surfaces.

FIG. 2 to FIGS. 12A and 12B show top-emission display units as examples.

Although this embodiment mainly describes a display unit including alight-emitting device that emits visible light and a light-receivingdevice that senses visible light, the display unit may also include alight-emitting device that emits infrared light. The light-receivingdevice may be configured to sense infrared light or sense both visiblelight and infrared light.

[Display Unit 10]

FIG. 2 is a cross-sectional view of a display unit 10.

The display unit 10 includes a light-receiving device 110 and alight-emitting device 190.

The light-emitting device 190 includes a pixel electrode 191, a bufferlayer 192, a light-emitting layer 193, a buffer layer 194, and a commonelectrode 115. The light-emitting layer 193 contains an organiccompound. The light-emitting device 190 has a function of emittingvisible light. Note that the display unit 10 may also include alight-emitting device having a function of emitting infrared light. Inthis embodiment, the case where the pixel electrode 191 functions as ananode and the common electrode 115 functions as a cathode is describedas an example.

The light-receiving device 110 includes a pixel electrode 181, a bufferlayer 182, an active layer 183, a buffer layer 184, and the commonelectrode 115. The active layer 183 contains an organic compound. Thelight-receiving device 110 has a function of sensing visible light. Notethat the light-receiving device 110 may also have a function of sensinginfrared light. This embodiment describes the light-receiving device 110in which the pixel electrode 181 functions as an anode and the commonelectrode 115 functions as a cathode to match the electrodes of thelight-emitting device 190. In other words, the light-receiving device110 is driven by application of reverse bias between the pixel electrode181 and the common electrode 115, whereby the display unit 10 can senselight incident on the light-receiving device 110, generate electriccharge, and extract it as current.

The pixel electrode 181, the pixel electrode 191, the buffer layer 182,the buffer layer 192, the active layer 183, the light-emitting layer193, the buffer layer 184, the buffer layer 194, and the commonelectrode 115 may each have a single-layer structure or a stacked-layerstructure.

The pixel electrode 181 and the pixel electrode 191 are positioned overan insulating layer 214. The pixel electrode 181 and the pixel electrode191 can be formed using the same material in the same step. An endportion of the pixel electrode 181 and an end portion of the pixelelectrode 191 are covered with a partition 216. The pixel electrode 181and the pixel electrode 191 are electrically isolated (electricallyseparated) from each other by the partition 216.

An organic insulating film is suitable for the partition 216. Examplesof materials that can be used for the organic insulating film include anacrylic resin, a polyimide resin, an epoxy resin, a polyamide resin, apolyimide-amide resin, a siloxane resin, a benzocyclobutene-based resin,a phenol resin, and precursors of these resins. The partition 216 is alayer that transmits visible light. Although the details will bedescribed later, a partition 217 that blocks visible light may beprovided instead of the partition 216.

The buffer layer 182 is positioned over the pixel electrode 181. Theactive layer 183 overlaps with the pixel electrode 181 with the bufferlayer 182 therebetween. The buffer layer 184 is positioned over theactive layer 183. The active layer 183 overlaps with the commonelectrode 115 with the buffer layer 184 therebetween. The buffer layer182 can include a hole-transport layer. The buffer layer 184 can includean electron-transport layer.

The buffer layer 192 is positioned over the pixel electrode 191. Thelight-emitting layer 193 overlaps with the pixel electrode 191 with thebuffer layer 192 therebetween. The buffer layer 194 is positioned overthe light-emitting layer 193. The light-emitting layer 193 overlaps withthe common electrode 115 with the buffer layer 194 therebetween. Thebuffer layer 192 can include one or both of a hole-injection layer and ahole-transport layer. The buffer layer 194 can include one or both of anelectron-injection layer and an electron-transport layer.

The common electrode 115 is a layer shared by the light-receiving device110 and the light-emitting device 190.

The material, thickness, and the like of the pair of electrodes can bethe same between the light-receiving device 110 and the light-emittingdevice 190. Thus, the manufacturing cost of the display unit can bereduced, and the manufacturing process of the display unit can besimplified.

The display unit 10 includes the light-receiving device 110, thelight-emitting device 190, a transistor 41, a transistor 42, and thelike between a pair of substrates (a substrate 151 and a substrate 152).

In the light-receiving device 110, the buffer layer 182, the activelayer 183, and the buffer layer 184, which are positioned between thepixel electrode 181 and the common electrode 115, can each be referredto as an organic layer (a layer containing an organic compound). Thepixel electrode 181 preferably has a function of reflecting visiblelight. The common electrode 115 has a function of transmitting visiblelight. Note that in the case where the light-receiving device 110 isconfigured to sense infrared light, the common electrode 115 has afunction of transmitting infrared light. Furthermore, the pixelelectrode 181 preferably has a function of reflecting infrared light.

The light-receiving device 110 has a function of sensing light.Specifically, the light-receiving device 110 is a photoelectricconversion device that receives light 22 incident from the outside ofthe display unit 10 and converts the light 22 into an electric signal.The light 22 can also be expressed as light that is emitted from thelight-emitting device 190 and then reflected by an object. The light 22may enter the light-receiving device 110 through a lens described later.

In the light-emitting device 190, the buffer layer 192, thelight-emitting layer 193, and the buffer layer 194, which are positionedbetween the pixel electrode 191 and the common electrode 115, can becollectively referred to as an EL layer. Note that the EL layer includesat least a light-emitting layer. The pixel electrode 191 preferably hasa function of reflecting visible light. The common electrode 115 has afunction of transmitting visible light. Note that when the display unit10 includes a light-emitting device that emits infrared light, thecommon electrode 115 has a function of transmitting infrared light.Furthermore, the pixel electrode 191 preferably has a function ofreflecting infrared light.

The light-emitting device included in the display unit of thisembodiment preferably employs a microcavity structure. Therefore, one ofthe pair of electrodes of the light-emitting device is preferably anelectrode having properties of transmitting and reflecting visible light(a transflective electrode), and the other is preferably an electrodehaving a property of reflecting visible light (a reflective electrode).When the light-emitting device has a microcavity structure, lightobtained from the light-emitting layer can be resonated between theelectrodes, whereby light emitted from the light-emitting device can beintensified.

Note that the transflective electrode can have a stacked-layer structureof a reflective electrode and an electrode having a property oftransmitting visible light (also referred to as a light-transmittingelectrode). In this specification and the like, the reflective electrodefunctioning as part of a transflective electrode may be referred to as apixel electrode or a common electrode, and the light-transmittingelectrode may be referred to as an optical adjustment layer; in somecases, the light-transmitting electrode (optical adjustment layer) canalso be regarded as having a function of a pixel electrode or a commonelectrode.

The light-transmitting electrode has a visible light transmittance ofhigher than or equal to 40%. For example, the light-emitting devicepreferably includes an electrode having a visible light (light atwavelengths greater than or equal to 400 nm and less than 750 nm)transmittance of higher than or equal to 40%. The visible lightreflectivity of the transflective electrode is higher than or equal to10% and less than or equal to 95%, preferably higher than or equal to30% and lower than or equal to 80%. The visible light reflectivity ofthe reflective electrode is higher than or equal to 40% and lower thanor equal to 100%, preferably higher than or equal to 70% and lower thanor equal to 100%. These electrodes preferably have a resistivity of1×10′ 2 cm or less. Note that in the case where a light-emitting devicethat emits infrared light is used in the display unit, the infraredlight (light at wavelengths from 750 nm 1300 nm) transmittance andreflectivity of these electrodes are preferably in the above ranges.

The buffer layer 192 or the buffer layer 194 may function as an opticaladjustment layer. By changing the thickness of the buffer layer 192 orthe buffer layer 194, light of a specific color can be intensified andtaken out from each light-emitting device. Note that when thetransflective electrode has a stacked-layer structure of a reflectiveelectrode and a light-transmitting electrode, the optical path lengthbetween the pair of electrodes represents the optical path lengthbetween a pair of reflective electrodes.

The light-emitting device 190 has a function of emitting visible light.

Specifically, the light-emitting device 190 is an electroluminescentdevice that emits light toward the substrate 152 (see emitted light 21)when voltage is applied between the pixel electrode 191 and the commonelectrode 115.

It is preferable that the light-emitting layer 193 be formed not tooverlap with the light-receiving device 110. Accordingly, it is possibleto prevent the light-emitting layer 193 from absorbing the light 22,thereby increasing the amount of light with which the light-receivingdevice 110 is irradiated.

The pixel electrode 181 is electrically connected to a source or a drainof the transistor 41 through an opening provided in the insulating layer214.

The pixel electrode 191 is electrically connected to a source or a drainof the transistor 42 through an opening provided in the insulating layer214. The transistor 42 has a function of controlling the driving of thelight-emitting device 190.

The transistor 41 and the transistor 42 are on and in contact with thesame layer (the substrate 151 in FIG. 2 ).

At least part of a circuit electrically connected to the light-receivingdevice 110 is preferably formed using the same material in the samesteps as a circuit electrically connected to the light-emitting device190. Thus, the thickness of the display unit can be reduced and themanufacturing process can be simplified, compared to the case where thetwo circuits are separately formed.

The light-receiving device 110 and the light-emitting device 190 arepreferably covered with a protective layer 116. In FIG. 2 , theprotective layer 116 is provided on and in contact with the commonelectrode 115. Providing the protective layer 116 can inhibit entry ofimpurities such as water into the light-receiving device 110 and thelight-emitting device 190, thereby increasing the reliability of thelight-receiving device 110 and the light-emitting device 190. Theprotective layer 116 and the substrate 152 are attached to each otherwith an adhesive layer 142.

A light-blocking layer 158 is provided on a surface of the substrate 152on the substrate 151 side. The light-blocking layer 158 has an openingat the position overlapping with the light-emitting device 190 and anopening at the position overlapping with the light-receiving device 110.Note that in this specification and the like, the position overlappingwith the light-emitting device 190 refers specifically to a positionoverlapping with a light-emitting region of the light-emitting device190. Similarly, the position overlapping with the light-receiving device110 refers specifically to a position overlapping with a light-receivingregion of the light-receiving device 110.

Here, the light-receiving device 110 senses light that is emitted fromthe light-emitting device 190 and then reflected by an object. However,in some cases, light emitted from the light-emitting device 190 isreflected inside the display unit 10 and enters the light-receivingdevice 110 without via an object. The light-blocking layer 158 canreduce the influence of such stray light. For example, in the case wherethe light-blocking layer 158 is not provided, light 23 emitted from thelight-emitting device 190 is reflected by the substrate 152 andreflected light 24 enters the light-receiving device 110 in some cases.Providing the light-blocking layer 158 can inhibit entry of thereflected light 24 into the light-receiving device 110. Thus, noise canbe reduced, and the sensitivity of the sensor using the light-receivingdevice 110 can be increased.

For the light-blocking layer 158, a material that blocks light from thelight-emitting device can be used. The light-blocking layer 158preferably absorbs visible light. As the light-blocking layer 158, ablack matrix can be formed using a metal material or a resin materialcontaining pigment (e.g., carbon black) or dye, for example. Thelight-blocking layer 158 may have a stacked-layer structure of a redcolor filter, a green color filter, and a blue color filter.

[Display Unit 10A]

FIG. 3A is a cross-sectional view of a display unit 10A. Note that inthe following description of display units, the description ofcomponents similar to those of the above-described display unit may beomitted.

The display unit 10A is different from the display unit 10 in includinga resin layer 159.

The resin layer 159 is provided on a surface of the substrate 152 on thesubstrate 151 side. The resin layer 159 is provided at the positionoverlapping with the light-emitting device 190 and is not provided atthe position overlapping with the light-receiving device 110.

The resin layer 159 can be provided at the position overlapping with thelight-emitting device 190 and have an opening 159 p at the positionoverlapping with the light-receiving device 110, as illustrated in FIG.3B, for example. As another example, as illustrated in FIG. 3C, anisland-shaped resin layer 159 can be provided at the positionoverlapping with the light-emitting device 190 but not at the positionoverlapping with the light-receiving device 110.

The light-blocking layer 158 is provided on surfaces of the substrate152 and the resin layer 159 on the substrate 151 side. Thelight-blocking layer 158 has an opening at the position overlapping withthe light-emitting device 190 and an opening at the position overlappingwith the light-receiving device 110.

For example, the light-blocking layer 158 can absorb stray light 23 athat has passed through the resin layer 159 and has been reflected bythe surface of the substrate 152 on the substrate 151 side. Moreover,the light-blocking layer 158 can absorb stray light 23 b before thestray light 23 b reaches the resin layer 159. Thus, stray light incidenton the light-receiving device 110 can be reduced. Consequently, noisecan be reduced, and the sensitivity of the sensor using thelight-receiving device 110 can be increased. It is particularlypreferable that the light-blocking layer 158 be positioned close to thelight-emitting device 190, in which case stray light can be furtherreduced. This is preferable also in terms of display quality, becausethe light-blocking layer 158 provided close to the light-emitting device190 can reduce viewing angle dependence of display.

Providing the light-blocking layer 158 can control the range where thelight-receiving device 110 senses light. When the light-blocking layer158 is positioned apart from the light-receiving device 110, the imagingrange is narrowed, and the imaging resolution can be increased.

In the case where the resin layer 159 has an opening, the light-blockinglayer 158 preferably covers at least part of the opening and at leastpart of a side surface of the resin layer 159 exposed in the opening.

In the case where the resin layer 159 is provided in an island shape,the light-blocking layer 158 preferably covers at least part of a sidesurface of the resin layer 159.

Since the light-blocking layer 158 is provided along the shape of theresin layer 159 in such a manner, the distance from the light-blockinglayer 158 to the light-emitting device 190 (specifically, thelight-emitting region of the light-emitting device 190) is shorter thanthe distance from the light-blocking layer 158 to the light-receivingdevice 110 (specifically, the light-receiving region of thelight-receiving device 110). Accordingly, noise of the sensor can bereduced, the imaging resolution can be increased, and viewing angledependence of display can be reduced. Thus, both the display quality andimaging quality of the display unit can be increased.

The resin layer 159 transmits light emitted from the light-emittingdevice 190. Examples of materials for the resin layer 159 include anacrylic resin, a polyimide resin, an epoxy resin, a polyamide resin, apolyimide-amide resin, a siloxane resin, a benzocyclobutene-based resin,a phenol resin, and precursors of these resins. Note that a componentprovided between the substrate 152 and the light-blocking layer 158 isnot limited to the resin layer and may be an inorganic insulating filmor the like. As the component becomes thicker, a larger differenceoccurs between the distance from the light-blocking layer to thelight-receiving device and the distance from the light-blocking layer tothe light-emitting device. An organic insulating film made of a resin orthe like is suitable for the component because it is easily formed tohave a large thickness.

In order to compare the distance from the light-blocking layer 158 tothe light-receiving device 110 and the distance from the light-blockinglayer 158 to the light-emitting device 190, it is possible to use, forexample, the shortest distance L1 from an end portion of thelight-blocking layer 158 on the light-receiving device 110 side to thecommon electrode 115 and the shortest distance L2 from an end portion ofthe light-blocking layer 158 on the light-emitting device 190 side tothe common electrode 115. With the shortest distance L2 smaller than theshortest distance L1, generation of stray light from the light-emittingdevice 190 can be suppressed, and the sensitivity of the sensor usingthe light-receiving device 110 can be increased. Furthermore, viewingangle dependence of display can be reduced. With the shortest distanceL1 larger than the shortest distance L2, the imaging range of thelight-receiving device 110 can be narrowed, and the imaging resolutioncan be increased.

In addition, when the adhesive layer 142 is provided such that a portionoverlapping with the light-receiving device 110 is made thicker than aportion overlapping with the light-emitting device 190, a difference canbe made between the distance from the light-blocking layer 158 to thelight-receiving device 110 and the distance from the light-blockinglayer 158 to the light-emitting device 190.

[Display Unit 10B]

FIG. 4A is a cross-sectional view of a display unit 10B.

The display unit 10B is different from the display unit TOA in that thedisplay unit 10B includes neither the buffer layer 182 nor the bufferlayer 192 but includes a common layer 112.

The common layer 112 is positioned over the partition 216, the pixelelectrode 181, and the pixel electrode 191. The common layer 112 isshared by the light-receiving device 110 and the light-emitting device190. The common layer 112 may have a single-layer structure or astacked-layer structure.

As the common layer 112, one or both of a hole-injection layer and ahole-transport layer can be formed, for example. A function of thecommon layer 112 in the light-emitting device 190 may be different fromits function in the light-receiving device 110. For example, when thecommon layer 112 includes a hole-injection layer, the hole-injectionlayer functions as a hole-injection layer in the light-emitting device190 and functions as a hole-transport layer in the light-receivingdevice 110.

It is preferred that at least one of the layers other than the activelayer and the light-emitting layer be shared by the light-receivingdevice and the light-emitting device, in which case the number of stepsof manufacturing the display unit can be reduced.

[Display Unit 10C]

FIG. 4B is a cross-sectional view of a display unit 10C.

The display unit 10C is different from the display unit 10A in that thedisplay unit 10C includes neither the buffer layer 184 nor the bufferlayer 194 but includes a common layer 114.

The common layer 114 is positioned over the partition 216, the activelayer 183, and the light-emitting layer 193. The common layer 114 isshared by the light-receiving device 110 and the light-emitting device190. The common layer 114 may have a single-layer structure or astacked-layer structure.

As the common layer 114, one or both of an electron-injection layer andan electron-transport layer can be formed, for example. A function ofthe common layer 114 in the light-emitting device 190 may be differentfrom its function in the light-receiving device 110. For example, whenthe common layer 114 includes an electron-injection layer, theelectron-injection layer functions as an electron-injection layer in thelight-emitting device 190 and functions as an electron-transport layerin the light-receiving device 110.

It is preferred that at least one of the layers other than the activelayer and the light-emitting layer be shared by the light-receivingdevice and the light-emitting device, in which case the number of stepsof manufacturing the display unit can be reduced.

[Display Unit 10D]

FIG. 5A is a cross-sectional view of a display unit 10D.

The display unit 10D is different from the display unit 10A in that thedisplay unit 10D does not include the buffer layer 182, the buffer layer192, the buffer layer 184, and the buffer layer 194 and includes thecommon layer 112 and the common layer 114.

In the display unit of this embodiment, an organic compound is used forthe active layer 183 of the light-receiving device 110. In thelight-receiving device 110, the layers other than the active layer 183can be common to the layers in the light-emitting device 190 (ELdevice). Therefore, the light-receiving device 110 can be formedconcurrently with the formation of the light-emitting device 190 only byadding a step of forming the active layer 183 in the manufacturingprocess of the light-emitting device 190. The light-emitting device 190and the light-receiving device 110 can be formed over one substrate.Accordingly, the light-receiving device 110 can be incorporated into thedisplay unit without a significant increase in the number ofmanufacturing steps.

The display unit 10D shows an example in which the light-receivingdevice 110 and the light-emitting device 190 have a common structureexcept that the active layer 183 of the light-receiving device 110 andthe light-emitting layer 193 of the light-emitting device 190 areseparately formed. Note that the structures of the light-receivingdevice 110 and the light-emitting device 190 are not limited thereto.The light-receiving device 110 and the light-emitting device 190 mayinclude a separately formed layer other than the active layer 183 andthe light-emitting layer 193 (see the display units 10A, 10B, and 10C).The light-receiving device 110 and the light-emitting device 190preferably include at least one layer used in common (common layer).Thus, the light-receiving device 110 can be incorporated into thedisplay unit without a significant increase in the number ofmanufacturing steps.

[Display Unit 10E]

FIG. 5B is a cross-sectional view of a display unit 10E.

The display unit TOE differs from the display unit 10D in that thedisplay unit TOE includes neither the substrate 151 nor the substrate152 and includes a substrate 153, a substrate 154, an adhesive layer155, and an insulating layer 212.

The substrate 153 and the insulating layer 212 are attached to eachother with the adhesive layer 155. The substrate 154 and the protectivelayer 116 are attached to each other with the adhesive layer 142.

The display unit TOE is formed in such a manner that the insulatinglayer 212, the transistor 41, the transistor 42, the light-receivingdevice 110, the light-emitting device 190, and the like that are formedover a formation substrate are transferred onto the substrate 153. Thesubstrate 153 and the substrate 154 are preferably flexible.Accordingly, the flexibility of the display unit 10E can be increased.For example, a resin is preferably used for the substrate 153 and thesubstrate 154.

For the substrate 153 and the substrate 154, any of the following can beused, for example: polyester resins such as polyethylene terephthalate(PET) and polyethylene naphthalate (PEN), a polyacrylonitrile resin, anacrylic resin, a polyimide resin, a polymethyl methacrylate resin, apolycarbonate (PC) resin, a polyethersulfone (PES) resin, polyamideresins (e.g., nylon and aramid), a polysiloxane resin, a cycloolefinresin, a polystyrene resin, a polyamide-imide resin, a polyurethaneresin, a polyvinyl chloride resin, a polyvinylidene chloride resin, apolypropylene resin, a polytetrafluoroethylene (PTFE) resin, an ABSresin, and cellulose nanofiber. Glass that is thin enough to haveflexibility may be used for one or both of the substrates 153 and 154.

As the substrate included in the display unit of this embodiment, a filmhaving high optical isotropy may be used. Examples of the film havinghigh optical isotropy include a triacetyl cellulose (TAC, also referredto as cellulose triacetate) film, a cycloolefin polymer (COP) film, acycloolefin copolymer (COC) film, and an acrylic film.

[Display Units 10F, 10G, and 10H]

FIG. 5C is a cross-sectional view of a display unit 10F. FIG. 6A is across-sectional view of a display unit 10G. FIG. 6B is a cross-sectionalview of a display unit 10H.

The display unit 10F includes a lens 149 in addition to the componentsof the display unit 10D.

The display unit of this embodiment may include the lens 149. The lens149 is provided at the position overlapping with the light-receivingdevice 110. In the display unit 10F, the lens 149 is provided in contactwith the substrate 152. The lens 149 included in the display unit 10Fhas a convex surface facing the substrate 151.

In the case where the light-blocking layer 158 and the lens 149 areformed on the same surface of the substrate 152, their formation orderis not limited. FIG. 5C illustrates an example in which the lens 149 isformed first; alternatively, the light-blocking layer 158 may be formedfirst. In FIG. 5C, an end portion of the lens 149 is covered with thelight-blocking layer 158.

In the display unit 10F, the light 22 enters the light-receiving device110 through the lens 149. With the lens 149, the imaging range of thelight-receiving device 110 can be narrowed as compared to the case wherethe lens 149 is not provided, thereby inhibiting overlap between theimaging ranges of the adjacent light-receiving devices 110. Thus, aclear image with little blurring can be captured. Given that the imagingrange of the light-receiving device 110 does not change, the lens 149allows the size of a pinhole (corresponding to the size of an opening inthe light-blocking layer 158 that overlaps with the light-receivingdevice 110 in FIG. 5C) to be increased, compared to the case where thelens 149 is not provided. Hence, providing the lens 149 can increase theamount of light entering the light-receiving device 110.

Like the display unit 10F, the display unit 10G illustrated in FIG. 6Ahas a structure in which the light 22 enters the light-receiving device110 through the lens 149.

In the display unit 10G, the lens 149 is provided in contact with a topsurface of the protective layer 116. The lens 149 included in thedisplay unit 10G has a convex surface facing the substrate 152.

In the display unit 10H illustrated in FIG. 6B, a lens array 146 isprovided on the display surface side of the substrate 152. A lensincluded in the lens array 146 is provided at the position overlappingwith the light-receiving device 110. The light-blocking layer 158 ispreferably provided on the surface of the substrate 152 on the substrate151 side.

As a method for forming the lens used in the display unit of thisembodiment, a lens such as a microlens may be formed directly over thesubstrate or the light-receiving device, or a lens array formedseparately, such as a microlens array, may be attached to the substrate.

The lens preferably has a refractive index of greater than or equal to1.3 and less than or equal to 2.5. The lens can be formed using at leastone of an inorganic material and an organic material. For example, amaterial containing a resin can be used for the lens. Moreover, amaterial containing at least one of an oxide and a sulfide can be usedfor the lens.

Specifically, a resin containing chlorine, bromine, or iodine, a resincontaining a heavy metal atom, a resin having an aromatic ring, a resincontaining sulfur, and the like can be used for the lens. Alternatively,a material containing a resin and nanoparticles of a material having ahigher refractive index than the resin can be used for the lens.Titanium oxide, zirconium oxide, and the like can be used for thenanoparticles.

In addition, cerium oxide, hafnium oxide, lanthanum oxide, magnesiumoxide, niobium oxide, tantalum oxide, titanium oxide, yttrium oxide,zinc oxide, an oxide containing indium and tin, an oxide containingindium, gallium, and zinc, and the like can be used for the lens.Alternatively, zinc sulfide and the like can be used for the lens.

[Display Unit 10J]

FIG. 6C is a cross-sectional view of a display unit 10J.

The display unit 10J is different from the display unit 10D in that thedisplay unit 10J does not include the partition 216 that transmitsvisible light but includes the partition 217 that blocks visible light.

The partition 217 preferably absorbs light emitted from thelight-emitting device 190. As the partition 217, a black matrix can beformed using a resin material containing a pigment or dye, for example.Moreover, the partition 217 can be formed of a colored insulating layerby using a brown resist material.

In the display unit 10D (FIG. 5A), in some cases, light emitted from thelight-emitting device 190 is reflected by the substrate 152 and thepartition 216, and the reflected light enters the light-receiving device110. In other cases, light emitted from the light-emitting device 190passes through the partition 216 and is reflected by the transistor, awiring, or the like, and thus the reflected light enters thelight-receiving device 110. In the display unit 10J, such reflectedlight can be prevented from entering the light-receiving device 110because light is absorbed by the partition 217. Hence, noise can bereduced, and the sensitivity of the sensor using the light-receivingdevice 110 can be increased.

The partition 217 preferably absorbs at least a wavelength of light thatis sensed by the light-receiving device 110. For example, in the casewhere the light-receiving device 110 senses green light emitted from thelight-emitting device 190, the partition 217 preferably absorbs at leastgreen light. For example, when the partition 217 includes a red colorfilter, the partition 217 can absorb green light and thus reflectedlight can be prevented from entering the light-receiving device 110.

Although the light-blocking layer 158 can absorb most of the stray light23 b before the stray light 23 b reaches the resin layer 159, part ofthe stray light 23 b may be reflected and enter the partition 217. Whenthe partition 217 is configured to absorb the stray light 23 b, thestray light 23 b can be prevented from entering the transistor, thewiring, or the like. Thus, stray light 23 c can be prevented fromreaching the light-receiving device 110. With a larger number of timesthe stray light 23 b strikes the light-blocking layer 158 and thepartition 217, the amount of absorbed light can be increased and theamount of the stray light 23 c reaching the light-receiving device 110can be extremely small. The resin layer 159 is preferably thick, inwhich case the number of times the stray light 23 b strikes thelight-blocking layer 158 and the partition 217 can be increased.

Since the partition 217 absorbs light, stray light 23 d that enters thepartition 217 directly from the light-emitting device 190 can beabsorbed by the partition 217. This also demonstrates that providing thepartition 217 can reduce the amount of stray light incident on thelight-receiving device 110.

[Display Unit 10K]

FIG. 7A is atop view of a display unit 10K. FIG. 7B is across-sectionalview along the dashed-dotted line A1-A2 in FIG. 7A. FIG. 8A isacross-sectional view along the dashed-dotted line A3-A4 in FIG. 7A.

In FIG. 7A, a portion surrounded by a dotted frame corresponds to onepixel. One pixel includes the light-receiving device 110, a redlight-emitting device 190R, a green light-emitting device 190G, and ablue light-emitting device 190B.

There is no particular limitation on the top surface shapes of thelight-receiving device 110 and the light-emitting devices 190R, 190G,and 190B. In the pixel layout illustrated in FIG. 7A, a hexagonalclose-packed arrangement is employed. The hexagonal close-packedarrangement is preferable because the fill factors of thelight-receiving device 110 and the light-emitting devices 190R, 190G,and 190 can be increased. In the top view, the light-emitting region ofthe light-receiving device 110 is quadrilateral, and the light-emittingregion of each of the light-emitting devices 190R, 190G, and 190B ishexagonal.

In the top view (also referred to as plan view), the light-receivingdevice 110 is provided on the inner side of a frame-shapedlight-blocking layer 219 a. The four sides of the light-receiving device110 are completely surrounded by the light-blocking layer 219 a, therebyinhibiting entry of stray light into the light-receiving device 110.Note that the frame-shaped light-blocking layer 219 a may have a gap(also referred to as a space, a disconnected portion, or a missingportion).

In the top view, a spacer 219 b is provided between the greenlight-emitting device 190G and the blue light-emitting device 190B.

As illustrated in FIG. 7B and FIG. 8A, the display unit 10K includes thelight-receiving device 110, the red light-emitting device 190R, thegreen light-emitting device 190G, and the blue light-emitting device190B.

The light-emitting device 190R includes a pixel electrode 191R, thecommon layer 112, a light-emitting layer 193R, the common layer 114, andthe common electrode 115. The light-emitting layer 193R contains anorganic compound that emits red light 21R. The light-emitting device190R has a function of emitting red light.

The light-emitting device 190G includes a pixel electrode 191G, thecommon layer 112, a light-emitting layer 193G, the common layer 114, andthe common electrode 115. The light-emitting layer 193G contains anorganic compound that emits green light 21G. The light-emitting device190G has a function of emitting green light.

The light-emitting device 190B includes a pixel electrode 191B, thecommon layer 112, a light-emitting layer 193B, the common layer 114, andthe common electrode 115. The light-emitting layer 193B contains anorganic compound that emits blue light 21B. The light-emitting device190B has a function of emitting blue light.

The light-receiving device 110 includes the pixel electrode 181, thecommon layer 112, the active layer 183, the common layer 114, and thecommon electrode 115. The active layer 183 contains an organic compound.The light-receiving device 110 has a function of sensing visible light.

In the display unit 10K, the light-receiving device 110, thelight-emitting device 190R, the light-emitting device 190G, thelight-emitting device 190B, the transistor 41, a transistor 42R, atransistor 42G, a transistor 42B, and the like are provided between apair of substrates (the substrate 151 and the substrate 152).

End portions of the pixel electrodes 181, 191R, 191G, and 191B arecovered with the partition 216.

The pixel electrode 181 is electrically connected to the source or thedrain of the transistor 41 through an opening provided in the insulatinglayer 214. The pixel electrode 191R is electrically connected to asource or a drain of the transistor 42R through an opening provided inthe insulating layer 214. Similarly, the pixel electrode 191G iselectrically connected to a source or a drain of the transistor 42Gthrough an opening provided in the insulating layer 214. The pixelelectrode 191B is electrically connected to a source or a drain of thetransistor 42B through an opening provided in the insulating layer 214.

The light-receiving device 110 and the light-emitting devices 190R,190G, and 190B are covered with the protective layer 116.

The resin layer 159 is provided on a surface of the substrate 152 on thesubstrate 151 side. The resin layer 159 is provided at the positionsoverlapping with the light-emitting devices 190R, 190G, and 190B and isnot provided at the position overlapping with the light-receiving device110.

The light-blocking layer 158 is provided on the surfaces of thesubstrate 152 and the resin layer 159 on the substrate 151 side. Thelight-blocking layer 158 has openings at the positions overlapping withthe light-emitting devices 190R, 190G, and 190B and at the positionoverlapping with the light-receiving device 110.

In the top view, a frame-shaped opening is provided in the partition216. In FIG. 7B, the partition 216 has an opening between thelight-receiving device 110 and the light-emitting device 190R. Thelight-blocking layer 219 a is provided to cover the opening. Thelight-blocking layer 219 a preferably covers the opening of thepartition 216 and a side surface of the partition 216 exposed in theopening. Furthermore, the light-blocking layer 219 a preferably coversat least part of a top surface of the partition 216.

Although the light-blocking layer 219 a can be provided over thepartition 216 that does not have an opening, there is a possibility thatstray light passes through the partition 216 and enters thelight-receiving device 110. When the partition 216 has an opening andthe light-blocking layer 219 a is provided to fill the opening, straylight that passes through the partition 216 is absorbed by thelight-blocking layer 219 a in the opening of the partition 216. This caninhibit entry of stray light into to the light-receiving device 110.

The light-blocking layer 219 a preferably has a forward tapered shape.This can improve the coverage of the light-blocking layer 219 a with thefilms provided thereover (e.g., the common layer 112, the common layer114, the common electrode 115, and the protective layer 116).

The light-blocking layer 219 a preferably absorbs at least a wavelengthof light that is sensed by the light-receiving device 110. For example,in the case where the light-receiving device 110 senses green lightemitted from the light-emitting device 190G, the light-blocking layer219 a preferably absorbs at least green light. For example, when thelight-blocking layer 219 a includes a red color filter, thelight-blocking layer 219 a can absorb green light and thus reflectedlight can be prevented from entering the light-receiving device 110. Thelight-blocking layer 219 a may be a black matrix formed using a resinmaterial containing a pigment or dye, for example. The light-blockinglayer 219 a may have a stacked-layer structure of a red color filter, agreen color filter, and a blue color filter. Alternatively, as thelight-blocking layer 219 a, a colored insulating layer may be formedusing a brown resist material.

For example, when the light-receiving device 110 senses green lightemitted from the light-emitting device 190G, in some cases, lightemitted from the light-emitting device 190G is reflected by thesubstrate 152 and the partition 216, and the reflected light enters thelight-receiving device 110. In other cases, light emitted from thelight-emitting device 190G passes through the partition 216 and isreflected by the transistor, the wiring, or the like, and thus thereflected light enters the light-receiving device 110. In the displayunit 10K, such reflected light can be prevented from entering thelight-receiving device 110 because light is absorbed by thelight-blocking layer 158 and the light-blocking layer 219 a. Hence,noise can be reduced, and the sensitivity of the sensor using thelight-receiving device 110 can be increased.

For example, the light-blocking layer 158 can absorb most of the straylight 23 b before the stray light 23 b reaches the resin layer 159.Furthermore, even when part of the stray light 23 b is reflected by thelight-blocking layer 158, the light-blocking layer 219 a absorbs thestray light 23 b, thereby inhibiting entry of the stray light 23 b intothe transistor, the wiring, or the like. Thus, stray light can beprevented from reaching the light-receiving device 110. With a largernumber of times the stray light 23 b strikes the light-blocking layer158 and the light-blocking layer 219 a, the amount of absorbed light canbe increased and the amount of stray light reaching the light-receivingdevice 110 can be extremely small. The resin layer 159 is preferablythick, in which case the number of times the stray light 23 b strikesthe light-blocking layer 158 and the light-blocking layer 219 a can beincreased. The thick resin layer 159 is also preferable in terms ofdisplay quality, because a shorter distance from the light-blockinglayer 158 to the light-emitting device of each color can reduce viewingangle dependence of display.

Since the light-blocking layer 219 a absorbs light, the stray light 23 dthat enters the light-blocking layer 219 a directly from thelight-emitting device can be absorbed by the light-blocking layer 219 a.This also demonstrates that providing the light-blocking layer 219 a canreduce the amount of stray light incident on the light-receiving device110.

Providing the light-blocking layer 158 can control the range where thelight-receiving device 110 senses light. When the distance from thelight-blocking layer 158 to the light-receiving device 110 is long, theimaging range is narrowed, and the imaging resolution can be increased.

The spacer 219 b is positioned over the partition 216, and is positionedbetween the light-emitting device 190G and the light-emitting device190B in the top view. A top surface of the spacer 219 b is preferablycloser to the light-blocking layer 158 than a top surface of thelight-blocking layer 219 a is. When a thickness L3 of the light-blockinglayer 219 a is greater than or equal to a total thickness L4 of thepartition 216 and the spacer 219 b, the inside of the frame-shapedlight-blocking layer 219 a is not sufficiently filled with the adhesivelayer 142 in some cases, which might reduce the reliability of thelight-receiving device 110 or even the reliability of the display unit10K. Therefore, the total thickness L4 of the partition 216 and thespacer 219 b is preferably larger than the thickness L3 of thelight-blocking layer 219 a. Thus, the inside of the light-blocking layer219 a can be easily filled with the adhesive layer 142. As illustratedin FIG. 8A, the light-blocking layer 158 may be in contact with theprotective layer 116 (or the common electrode 115) in a portion wherethe spacer 219 b and the light-blocking layer 158 overlap with eachother.

[Display Unit 10L]

FIG. 8B is a cross-sectional view of a display unit 10L.

In the display unit 10L, the light-emitting devices 190R, 190G, and 190Binclude the same light-emitting layer. FIG. 8B corresponds to across-sectional view along the dashed-dotted line A3-A4 in FIG. 7A.

The light-emitting device 190G in FIG. 8B includes the pixel electrode191G, an optical adjustment layer 197G, the common layer 112, thelight-emitting layer 113, the common layer 114, and the common electrode115. The light-emitting device 190B in FIG. 8B includes the pixelelectrode 191B, an optical adjustment layer 197B, the common layer 112,the light-emitting layer 113, the common layer 114, and the commonelectrode 115. The common layer 112, the light-emitting layer 113, andthe common layer 114 are common components between the light-emittingdevices 190R, 190G, and 190B. The light-emitting layer 113 includes, forexample, the light-emitting layer 193R that emits red light, thelight-emitting layer 193G that emits green light, and the light-emittinglayer 193B that emits blue light.

Although the common layer 112, the light-emitting layer 113, and thecommon layer 114 are shown as the EL layer in FIG. 8B, this embodimentis not limited thereto. The light-emitting device may have a singlestructure (FIG. 18A) in which one EL layer is provided between the pixelelectrode and the common electrode, or a tandem structure (FIG. 18B) inwhich a plurality of EL layers are provided between the electrodes.

The light-emitting layer 113 is shared by the light-emitting devicesthat emit light of different colors. Light emitted from thelight-emitting device 190G is extracted as the green light 21G through acoloring layer CFG. Light emitted from the light-emitting device 190B isextracted as the blue light 21B through a coloring layer CFB.

The light-emitting device 190G and the light-emitting device 190B havethe same structure except that they include optical adjustment layerswith different thicknesses. A reflective electrode is used as the pixelelectrode 191G and the pixel electrode 191B. As the optical adjustmentlayer, a light-transmitting electrode over the reflective electrode canbe used. The thickness of the optical adjustment layer 197 preferablyvaries between the light-emitting devices of different colors. Thelight-emitting device 190G illustrated in FIG. 8B has been opticallyadjusted using the optical adjustment layer 197G so that the opticalpath length between the pixel electrode 191G and the common electrode115 intensifies green light. Similarly, the light-emitting device 190Bhas been optically adjusted using the optical adjustment layer 197B sothat the optical path length between the pixel electrode 191B and thecommon electrode 115 intensifies blue light.

[Display Unit 10M]

FIG. 9A is atop view of a display unit 10M. FIG. 9B is across-sectionalview along the dashed-dotted line A5-A6 in FIG. 9A.

The display unit 10M illustrated in FIGS. 9A and 9B is different fromthe display unit 10K illustrated in FIGS. 7A, 7B, and 8A in includingthe light-blocking layer 219 a between the green light-emitting device190G and the blue light-emitting device 190B and employing a hollowsealing structure in which a space 143 is filled with an inert gas.

As in the display unit 10M, the light-blocking layer 219 a may beprovided both between the light-emitting device 190R and thelight-receiving device 110 and between the light-emitting device 190Gand the light-emitting device 190B.

[Display Unit 10N]

FIG. 10A is a top view of a display unit 10N. FIG. 10B is across-sectional view along the dashed-dotted line A7-A8 in FIG. 10A.FIG. 11A is a cross-sectional view along the dashed-dotted line A9-A10in FIG. 10A.

As a cross-sectional structure of the display unit 10N (FIG. 10A) alongthe dashed-dotted line A3-A4, a structure similar to that of the displayunit 10K (FIG. 8A) can be employed. Alternatively, a structure similarto that of the display unit 10M (FIG. 9B) may be employed.

The top surface shape and the cross-sectional shape of thelight-blocking layer 219 a in the display unit 10N are different fromthose in the display unit 10K (FIGS. 7A and 7B).

In the top view (also referred to as plan view), the light-blockinglayer 219 a surrounds the four sides of the light-receiving device 110and has one end and the other end apart from each other. A gap 220 (alsoreferred to as space, disconnected portion, or missing portion) of thelight-blocking layer 219 a is positioned close to the red light-emittingdevice 190R. In the case where only a light-emitting device that emitslight of a specific color is used as a light source for sensing, the gap220 of the light-blocking layer 219 a is preferably positioned close toa light-emitting device different from the light-emitting device usedfor the sensing. For example, the display unit 10N is preferablyconfigured to perform sensing with the use of the green light-emittingdevice 190G or the blue light-emitting device 190B. Thus, an influenceof noise in the sensing can be suppressed. Moreover, in the case wheresensing is performed using the green light-emitting device 190G, it ispreferred that one end of the light-blocking layer 219 a extend towardthe red light-emitting device 190R more than toward the greenlight-emitting device 190G, as shown in a region 230. Accordingly, straylight from the green light-emitting device 190G can be prevented fromentering the light-receiving device 110 through the gap 220.

The partition 216 has an opening between the light-receiving device 110and the light-emitting device 190R. The light-blocking layer 219 a isprovided to cover the opening. The light-blocking layer 219 a preferablycovers the opening of the partition 216 and a side surface of thepartition 216 exposed in the opening. Furthermore, the light-blockinglayer 219 a preferably covers at least part of the top surface of thepartition 216.

The light-blocking layer 219 a may have an inversely tapered shape. Theorganic film and the common electrode 115 that are provided over theinversely tapered light-blocking layer 219 a may be thin around a sidesurface of the light-blocking layer 219 a. Furthermore, a space 160 issometimes generated around the side surface of the light-blocking layer219 a.

Here, if the light-blocking layer 219 a surrounds all the four sides ofthe light-receiving device 110 in the top view, the common electrode 115might be broken by the light-blocking layer 219 a and separated into aportion on the inner side of the light-blocking layer 219 a and aportion on the outer side thereof. In view of this, the gap 220 isprovided by making the light-blocking layer 219 a have a top surfaceshape such that the light-blocking layer 219 a surrounds the four sidesof the light-receiving device 110 and its one end is apart from theother end; hence, separation of the common electrode 115 can beinhibited. Consequently, a display defect in the display unit 10N can beinhibited.

FIG. 11A is a cross-sectional view including the gap 220 of thelight-blocking layer 219 a. In the top view, the partition 216 has anopening that surrounds the four sides of the light-receiving device 110and has one end and the other end apart from each other in a mannersimilar to the top surface shape of the light-blocking layer 219 a. Inthe gap 220 of the light-blocking layer 219 a, the common layer 112, thecommon layer 114, the common electrode 115, and the protective layer 116are provided in this order over the partition 216.

[Display Unit 10P]

FIG. 11B is a cross-sectional view of a display unit 10P.

The display unit 10P is different from the display unit 10N in includinga sidewall 219 c in contact with a side surface of the light-blockinglayer 219 a.

In the display unit 10P, the top surface of the light-blocking layer 219a may have a frame shape as illustrated in FIG. 7A or may have the gap220 as illustrated in FIG. 10A.

Providing the sidewall 219 c in contact with the side surface of theinversely tapered light-blocking layer 219 a makes it possible toimprove the coverage of the light-blocking layer 219 a with the organicfilm, the common electrode 115, and the like and increase the displayquality of the display unit. Improvement of the coverage of thelight-blocking layer 219 a with the common electrode 115 can preventbreakage or even thickness reduction of the common electrode 115,thereby inhibiting display luminance unevenness due to a voltage drop ofthe common electrode 115.

The sidewall 219 c can be formed using a material that can be used forthe partition 216.

[Display Unit 10Q]

FIGS. 12A and 12B are cross-sectional views of a display unit 10Q. Thedisplay unit 10Q can have a top surface structure similar to that of thedisplay unit 10K (FIG. 7A). FIG. 12A is a cross-sectional view along thedashed-dotted line A1-A2 in FIG. 7A. FIG. 12B is a cross-sectional viewtaken along the dashed-dotted line A3-A4 in FIG. 7A.

The display unit 10Q differs from the display unit 10K mainly in thatthe display unit 10Q does not include the partition 216 and includes thepartition 217.

The light-blocking layer 219 a is positioned over the partition 217.Unlike the partition 216, the partition 217 can absorb light emittedfrom the light-emitting device; hence, an opening does not need to beformed in the partition 217. The stray light 23 d that enters thepartition 217 from the light-emitting device is absorbed by thepartition 217. The stray light 23 d that enters the light-blocking layer219 a from the light-emitting device is absorbed by the light-blockinglayer 219 a.

The spacer 219 b is positioned between the light-emitting device 190Gand the light-emitting device 190B. The top surface of the spacer 219 bis preferably closer to the light-blocking layer 158 than the topsurface of the light-blocking layer 219 a is. When the spacer 219 b isthinner than the light-blocking layer 219 a, the inside of theframe-shaped light-blocking layer 219 a is not sufficiently filled withthe adhesive layer 142 in some cases, which might reduce the reliabilityof the light-receiving device 110 or even the reliability of the displayunit 10Q. Therefore, the spacer 219 b is preferably thicker than thelight-blocking layer 219 a. Thus, the inside of the light-blocking layer219 a can be easily filled with the adhesive layer 142. As illustratedin FIG. 12B, the light-blocking layer 158 may be in contact with theprotective layer 116 (or the common electrode 115) in a portion wherethe spacer 219 b and the light-blocking layer 158 overlap with eachother.

A more detailed structure of the display unit of one embodiment of thepresent invention will be described below with reference to FIG. 13 ,FIG. 14 , FIGS. 15A and 15B, FIG. 16 , and FIGS. 17A and 17B.

[Display Unit 100A]

FIG. 13 is a perspective view of a display unit 100A, and FIG. 14 is across-sectional view of the display unit 100A.

In the display unit 100A, the substrate 152 and the substrate 151 areattached to each other. In FIG. 13 , the substrate 152 is denoted by adashed line.

The display unit 100A includes a display portion 162, a circuit 164, awiring 165, and the like. FIG. 13 illustrates an example in which anintegrated circuit (IC) 173 and an FPC 172 are mounted on the displayunit 100A. Thus, the structure illustrated in FIG. 13 can be regarded asa display module including the display unit 100A, the IC, and the FPC.

As the circuit 164, a scan line driver circuit can be used, for example.

The wiring 165 has a function of supplying a signal and power to thedisplay portion 162 and the circuit 164. The signal and power are inputto the wiring 165 from the outside through the FPC 172 or from the IC173.

FIG. 13 illustrates an example in which the IC 173 is provided over thesubstrate 151 by a chip on glass (COG) method, a chip on film (COF)method, or the like. An IC including a scan line driver circuit, asignal line driver circuit, or the like can be used as the IC 173, forexample. Note that the display unit 100A and the display module are notnecessarily provided with an IC. The IC may be mounted on the FPC by aCOF method or the like.

FIG. 14 illustrates an example of cross sections of part of a regionincluding the FPC 172, part of the circuit 164, part of the displayportion 162, and part of a region including an end portion of thedisplay unit 100A.

The display unit 100A in FIG. 14 includes a transistor 201, a transistor205, a transistor 206, the light-emitting device 190, thelight-receiving device 110, and the like between the substrate 151 andthe substrate 152.

The resin layer 159 and the insulating layer 214 adhere to each otherwith the adhesive layer 142. A solid sealing structure, a hollow sealingstructure, or the like can be employed to seal the light-emitting device190 and the light-receiving device 110. In FIG. 14 , a hollow sealingstructure is employed in which the space 143 surrounded by the substrate152, the adhesive layer 142, and the substrate 151 is filled with aninert gas (e.g., nitrogen or argon). The adhesive layer 142 may beprovided to overlap with the light-emitting device 190 and thelight-receiving device 110. The space 143 surrounded by the substrate152, the adhesive layer 142, and the substrate 151 may be filled with aresin different from that of the adhesive layer 142.

The light-emitting device 190 has a stacked-layer structure in which thepixel electrode 191, the common layer 112, the light-emitting layer 193,the common layer 114, and the common electrode 115 are stacked in thisorder from the insulating layer 214 side. The pixel electrode 191 isconnected to a conductive layer 222 b included in the transistor 206through an opening provided in the insulating layer 214.

An end portion of the pixel electrode 191 is covered with the partition217. The pixel electrode 191 contains a material that reflects visiblelight, and the common electrode 115 contains a material that transmitsvisible light.

The light-receiving device 110 has a stacked-layer structure in whichthe pixel electrode 181, the common layer 112, the active layer 183, thecommon layer 114, and the common electrode 115 are stacked in this orderfrom the insulating layer 214 side. The pixel electrode 181 iselectrically connected to the conductive layer 222 b included in thetransistor 205 through an opening provided in the insulating layer 214.An end portion of the pixel electrode 181 is covered with the partition217. The pixel electrode 181 contains a material that reflects visiblelight, and the common electrode 115 contains a material that transmitsvisible light.

Light from the light-emitting device 190 is emitted toward the substrate152. Light enters the light-receiving device 110 through the substrate152 and the space 143. For the substrate 152, a material having a highvisible-light-transmitting property is preferably used.

The pixel electrode 181 and the pixel electrode 191 can be formed usingthe same material in the same step. The common layer 112, the commonlayer 114, and the common electrode 115 are used in both thelight-receiving device 110 and the light-emitting device 190. Thelight-receiving device 110 and the light-emitting device 190 can havecommon components except the active layer 183 and the light-emittinglayer 193. Thus, the light-receiving device 110 can be incorporated intothe display unit 100A without a significant increase in the number ofmanufacturing steps.

The resin layer 159 and the light-blocking layer 158 are provided on asurface of the substrate 152 on the substrate 151 side. The resin layer159 is provided at the position overlapping with the light-emittingdevice 190 and is not provided at the position overlapping with thelight-receiving device 110. The light-blocking layer 158 is provided tocover the surface of the substrate 152 on the substrate 151 side, a sidesurface of the resin layer 159, and a surface of the resin layer 159 onthe substrate 151 side. The light-blocking layer 158 has an opening atthe position overlapping with the light-receiving device 110 and anopening at the position overlapping with the light-emitting device 190.Providing the light-blocking layer 158 can control the range where thelight-receiving device 110 senses light. Moreover, providing thelight-blocking layer 158 can inhibit direct entry of light into thelight-receiving device 110 from the light-emitting device 190 withoutvia an object. Hence, a sensor with less noise and high sensitivity canbe obtained. Providing the resin layer 159 allows the distance from thelight-blocking layer 158 to the light-emitting device 190 to be shorterthan the distance from the light-blocking layer 158 to thelight-receiving device 110. Accordingly, viewing angle dependence ofdisplay can be reduced while noise of the sensor is reduced. Thus, boththe display quality and imaging quality can be increased.

The structures of the partition 217 and the light-blocking layer 219 ain the display unit 100A are similar to those in the display unit 10Q(FIG. 12A).

The partition 217 covers an end portion of the pixel electrode 181 andan end portion of the pixel electrode 191. The light-blocking layer 219a is provided over the partition 217. The light-blocking layer 219 a ispositioned between the light-receiving device 110 and the light-emittingdevice 190. The partition 217 and the light-blocking layer 219 apreferably absorb the wavelength of light that the light-receivingdevice 110 senses. This can reduce stray light entering thelight-receiving device 110.

The transistor 201, the transistor 205, and the transistor 206 areformed over the substrate 151. These transistors can be fabricated usingthe same material in the same step.

An insulating layer 211, an insulating layer 213, an insulating layer215, and the insulating layer 214 are provided in this order over thesubstrate 151. Part of the insulating layer 211 functions as a gateinsulating layer of each transistor. Part of the insulating layer 213functions as agate insulating layer of each transistor. The insulatinglayer 215 is provided to cover the transistors. The insulating layer 214is provided to cover the transistors and has a function of aplanarization layer. Note that the number of gate insulating layers andthe number of insulating layers covering the transistors are not limitedand may each be one or two or more.

A material through which impurities such as water and hydrogen do noteasily diffuse is preferably used for at least one of the insulatinglayers covering the transistors, in which case the insulating layer canfunction as a barrier layer. Such a structure can effectively inhibitdiffusion of impurities into the transistors from the outside andincrease the reliability of the display unit.

An inorganic insulating film is preferably used as each of theinsulating layers 211, 213, and 215. As the inorganic insulating film, asilicon nitride film, a silicon oxynitride film, a silicon oxide film, asilicon nitride oxide film, an aluminum oxide film, or an aluminumnitride film can be used, for example. A hafnium oxide film, an yttriumoxide film, a zirconium oxide film, a gallium oxide film, a tantalumoxide film, a magnesium oxide film, a lanthanum oxide film, a ceriumoxide film, a neodymium oxide film, or the like may be used. A stackincluding two or more of the above insulating films may also be used.

An organic insulating film often has a lower barrier property than aninorganic insulating film. Therefore, the organic insulating filmpreferably has an opening in the vicinity of an end portion of thedisplay unit 100A. This can inhibit entry of impurities from the endportion of the display unit 100A through the organic insulating film.Alternatively, the organic insulating film may be formed so that its endportions is positioned on the inner side compared to the end portion ofthe display unit 100A, to prevent the organic insulating film from beingexposed at the end portion of the display unit 100A.

An organic insulating film is suitable for the insulating layer 214functioning as a planarization layer. Examples of materials that can beused for the organic insulating film include an acrylic resin, apolyimide resin, an epoxy resin, a polyamide resin, a polyimide-amideresin, a siloxane resin, a benzocyclobutene-based resin, a phenol resin,and precursors of these resins.

In a region 228 illustrated in FIG. 14 , an opening is formed in theinsulating layer 214. This can inhibit entry of impurities into thedisplay portion 162 from the outside through the insulating layer 214even when an organic insulating film is used as the insulating layer214. Consequently, the reliability of the display unit 100A can beincreased.

Each of the transistors 201, 205, and 206 includes a conductive layer221 functioning as a gate, the insulating layer 211 functioning as agate insulating layer, a conductive layer 222 a and the conductive layer222 b functioning as a source and a drain, a semiconductor layer 231,the insulating layer 213 functioning as a gate insulating layer, and aconductive layer 223 functioning as a gate. Here, a plurality of layersobtained by processing the same conductive film are shown with the samehatching pattern. The insulating layer 211 is positioned between theconductive layer 221 and the semiconductor layer 231. The insulatinglayer 213 is positioned between the conductive layer 223 and thesemiconductor layer 231.

There is no particular limitation on the structure of the transistorsincluded in the display unit of this embodiment. For example, a planartransistor, a staggered transistor, or an inverted staggered transistorcan be used. A top-gate transistor or a bottom-gate transistor can beused. Alternatively, gates may be provided above and below asemiconductor layer where a channel is formed.

The transistors 201, 205, and 206 employ a structure in which thesemiconductor layer where a channel is formed is positioned between twogates. The two gates may be connected to each other and supplied withthe same signal to operate the transistor. Alternatively, the thresholdvoltage of the transistor may be controlled by supplying a potential forcontrolling the threshold voltage to one of the two gates and apotential for driving to the other.

There is no particular limitation on the crystallinity of asemiconductor material used in the transistor, and an amorphoussemiconductor or a semiconductor having crystallinity (amicrocrystalline semiconductor, a polycrystalline semiconductor, asingle crystal semiconductor, or a semiconductor partly includingcrystal regions) can be used. It is preferable to use a semiconductorhaving crystallinity, in which case degradation of the transistorcharacteristics can be suppressed.

The semiconductor layer of the transistor preferably contains a metaloxide (also referred to as an oxide semiconductor). Alternatively, thesemiconductor layer of the transistor may contain silicon. Examples ofsilicon include amorphous silicon and crystalline silicon (e.g.,low-temperature polysilicon and single crystal silicon).

The semiconductor layer preferably contains indium, M (M is one or morekinds selected from gallium, aluminum, silicon, boron, yttrium, tin,copper, vanadium, beryllium, titanium, iron, nickel, germanium,zirconium, molybdenum, lanthanum, cerium, neodymium, hafnium, tantalum,tungsten, and magnesium), and zinc, for example. Specifically, M ispreferably one or more kinds selected from aluminum, gallium, yttrium,and tin.

It is particularly preferable to use an oxide containing indium (In),gallium (Ga), and zinc (Zn) (also referred to as IGZO) for thesemiconductor layer.

When the semiconductor layer is an In-M-Zn oxide, the atomic ratio of Inis preferably greater than or equal to the atomic ratio of M in theIn-M-Zn oxide. Examples of the atomic ratio of the metal elements insuch an In-M-Zn oxide are In:M:Zn=1:1:1, 1:1:1.2, 2:1:3, 3:1:2, 4:2:3,4:2:4.1, 5:1:3, 5:1:6, 5:1:7, 5:1:8, 6:1:6, and 5:2:5 and a compositionin the vicinity of any of the above atomic ratios. Note that thevicinity of the atomic ratio includes ±30% of an intended atomic ratio.

For example, in the case of describing an atomic ratio of In:Ga:Zn=4:2:3or a composition in the vicinity thereof, the case is included in whichwith the atomic proportion of In being 4, the atomic proportion of Ga isgreater than or equal to 1 and less than or equal to 3 and the atomicproportion of Zn is greater than or equal to 2 and less than or equal to4. In the case of describing an atomic ratio of In:Ga:Zn=5:1:6 or acomposition in the vicinity thereof, the case is included in which withthe atomic proportion of In being 5, the atomic proportion of Ga isgreater than 0.1 and less than or equal to 2 and the atomic proportionof Zn is greater than or equal to 5 and less than or equal to 7. In thecase of describing anatomic ratio of In:Ga:Zn=1:1:1 or a composition inthe vicinity thereof, the case is included in which with the atomicproportion of In being 1, the atomic proportion of Ga is greater than0.1 and less than or equal to 2 and the atomic proportion of Zn isgreater than 0.1 and less than or equal to 2.

The transistor included in the circuit 164 and the transistor includedin the display portion 162 may have the same structure or differentstructures. One structure or two or more kinds of structures may beemployed for a plurality of transistors included in the circuit 164.Similarly, one structure or two or more kinds of structures may beemployed for a plurality of transistors included in the display portion162.

A connection portion 204 is provided in a region of the substrate 151where the substrate 152 does not overlap. In the connection portion 204,the wiring 165 is electrically connected to the FPC 172 through aconductive layer 166 and a connection layer 242. On the top surface ofthe connection portion 204, the conductive layer 166 obtained byprocessing the same conductive film as the pixel electrode 181 isexposed. Thus, the connection portion 204 and the FPC 172 can beelectrically connected to each other through the connection layer 242.

A variety of optical members can be arranged on the outer surface of thesubstrate 152. Examples of the optical members include a polarizingplate, a retardation plate, a light diffusion layer (e.g., a diffusionfilm), an anti-reflective layer, and a light-condensing film.Furthermore, an antistatic film preventing the attachment of dust, awater repellent film suppressing the attachment of stain, a hard coatfilm suppressing generation of a scratch caused by the use, animpact-absorbing layer, or the like may be arranged on the outer surfaceof the substrate 152.

For each of the substrates 151 and 152, glass, quartz, ceramic,sapphire, a resin, or the like can be used. When the substrates 151 and152 are formed using a flexible material, the flexibility of the displayunit can be increased.

As the adhesive layer, a variety of curable adhesives such as a reactivecurable adhesive, a thermosetting adhesive, an anaerobic adhesive, and aphotocurable adhesive such as an ultraviolet curable adhesive can beused. Examples of these adhesives include an epoxy resin, an acrylicresin, a silicone resin, a phenol resin, a polyimide resin, an imideresin, a polyvinyl chloride (PVC) resin, a polyvinyl butyral (PVB)resin, and an ethylene vinyl acetate (EVA) resin. In particular, amaterial with low moisture permeability, such as an epoxy resin, ispreferred. A two-component-mixture-type resin may be used. An adhesivesheet or the like may be used.

As the connection layer 242, an anisotropic conductive film (ACF), ananisotropic conductive paste (ACP), or the like can be used.

The light-emitting device 190 can have a top-emission structure, abottom-emission structure, a dual-emission structure, or the like. Aconductive film that transmits visible light is used as the electrodethrough which light is extracted. A conductive film that reflectsvisible light is preferably used as the electrode through which light isnot extracted.

The light-emitting device 190 includes at least the light-emitting layer193. In addition to the light-emitting layer 193, the light-emittingdevice 190 may further include one or more layers containing any of asubstance with a high hole-injection property, a substance with a highhole-transport property, a hole-blocking material, a substance with ahigh electron-transport property, a substance with a highelectron-injection property, a substance with a bipolar property (asubstance with a high electron- and hole-transport property), and thelike. For example, the common layer 112 preferably includes one or bothof a hole-injection layer and a hole-transport layer. For example, thecommon layer 114 preferably includes one or both of anelectron-transport layer and an electron-injection layer.

The hole-injection layer injects holes from an anode to thehole-transport layer and contains a material with a high hole-injectionproperty. As the material with a high hole-injection property, anaromatic amine compound and a composite material containing ahole-transport material and an acceptor material (electron-acceptingmaterial) can be used.

In the light-emitting device, the hole-transport layer transports holesthat are injected from the anode by the hole-injection layer, to thelight-emitting layer. In the light-receiving device, the hole-transportlayer transports holes that are generated in the active layer on thebasis of incident light, to the anode. The hole-transport layer containsa hole-transport material. The hole-transport material preferably has ahole mobility of 1×10⁻⁶ cm²/Vs or higher. Note that any other substancecan also be used as long as the substance has a hole-transport propertyhigher than an electron-transport property. As the hole-transportmaterial, materials having a high hole-transport property, such as aπ-electron rich heteroaromatic compound (e.g., a carbazole derivative, athiophene derivative, and a furan derivative) and an aromatic amine (acompound having an aromatic amine skeleton), are preferable.

In the light-emitting device, the electron-transport layer transportselectrons that are injected from the cathode by the electron-injectionlayer, to the light-emitting layer. In the light-receiving device, theelectron-transport layer transports electrons that are generated in theactive layer on the basis of incident light, to the cathode. Theelectron-transport layer contains an electron-transport material. Theelectron-transport material preferably has an electron mobility of1×10⁻⁶ cm²/Vs or higher. Note that any other substance can also be usedas long as the substance has an electron-transport property higher thana hole-transport property. As the electron-transport material, any ofthe following materials having a high electron-transport property can beused, for example: a metal complex having a quinoline skeleton, a metalcomplex having a benzoquinoline skeleton, a metal complex having anoxazole skeleton, a metal complex having a thiazole skeleton, anoxadiazole derivative, a triazole derivative, an imidazole derivative,an oxazole derivative, a thiazole derivative, a phenanthrolinederivative, a quinoline derivative having a quinoline ligand, abenzoquinoline derivative, a quinoxaline derivative, adibenzoquinoxaline derivative, a pyridine derivative, a bipyridinederivative, a pyrimidine derivative, and a π-electron deficientheteroaromatic compound such as a nitrogen-containing heteroaromaticcompound.

The electron-injection layer injects electrons from the cathode to theelectron-transport layer and contains a material with a highelectron-injection property. As the material with a highelectron-injection property, an alkali metal, an alkaline earth metal,or a compound thereof can be used. As the material with a highelectron-injection property, a composite material containing anelectron-transport material and a donor material (electron-donatingmaterial) can also be used.

Either a low molecular compound or a high molecular compound can be usedfor the common layer 112, the light-emitting layer 193, and the commonlayer 114, and an inorganic compound may also be contained. The layersincluded in the common layer 112, the light-emitting layer 193, and thecommon layer 114 can be formed by any of the following methods, forexample: an evaporation method (including a vacuum evaporation method),a transfer method, a printing method, an inkjet method, and a coatingmethod.

The light-emitting layer 193 contains a light-emitting substance. Thelight-emitting layer 193 can contain one or more kinds of light-emittingsubstances. As the light-emitting substance, a substance whose emissioncolor is blue, violet, bluish violet, green, yellowish green, yellow,orange, red, or the like is appropriately used. Alternatively, asubstance that emits infrared light can be used as the light-emittingsubstance.

The active layer 183 of the light-receiving device 110 contains asemiconductor. Examples of the semiconductor include an inorganicsemiconductor such as silicon and an organic semiconductor including anorganic compound. This embodiment shows an example in which an organicsemiconductor is used as the semiconductor included in the active layer.The use of an organic semiconductor is preferable because thelight-emitting layer 193 of the light-emitting device 190 and the activelayer 183 of the light-receiving device 110 can be formed by the samemethod (e.g., a vacuum evaporation method) and thus the samemanufacturing apparatus can be used.

Examples of an n-type semiconductor material included in the activelayer 183 are electron-accepting organic semiconductor materials such asfullerene (e.g., C₆₀ and C₇₀) and derivatives thereof. Examples of ap-type semiconductor material included in the active layer 183 areelectron-donating organic semiconductor materials such as copper(II)phthalocyanine (CuPc), tetraphenyldibenzoperiflanthene (DBP), and zincphthalocyanine (ZnPc). As a p-type semiconductor material, tinphthalocyanine (SnPc) may be used.

For example, the active layer 183 is preferably formed by co-evaporationof an n-type semiconductor and a p-type semiconductor.

As materials for the gates, the source, and the drain of a transistorand conductive layers functioning as wirings and electrodes included inthe display unit, any of metals such as aluminum, titanium, chromium,nickel, copper, yttrium, zirconium, molybdenum, silver, tantalum, andtungsten, or an alloy containing any of these metals as its maincomponent can be used. A single-layer structure or a stacked-layerstructure including a film containing any of these materials can beused.

As a light-transmitting conductive material, a conductive oxide such asindium oxide, indium tin oxide, indium zinc oxide, zinc oxide, or zincoxide containing gallium, or graphene can be used. It is also possibleto use a metal material such as gold, silver, platinum, magnesium,nickel, tungsten, chromium, molybdenum, iron, cobalt, copper, palladium,or titanium; an alloy material containing any of these metal materials;or a nitride of the metal material (e.g., titanium nitride). In the caseof using the metal material or the alloy material (or the nitridethereof), the thickness is preferably set small enough to be able totransmit light. Alternatively, a stacked film of any of the abovematerials can be used as the conductive layers. For example, a stackedfilm of indium tin oxide and an alloy of silver and magnesium ispreferably used, in which case the conductivity can be increased. Theabove materials can also be used for conductive layers functioning aswirings and electrodes included in the display unit and the conductivelayers of the display device (the conductive layers functioning as thepixel electrode and the common electrode).

Examples of insulating materials that can be used for the insulatinglayers include a resin material such as an acrylic resin and an epoxyresin, and an inorganic insulating material such as silicon oxide,silicon oxynitride, silicon nitride oxide, silicon nitride, and aluminumoxide.

[Display Unit 100B]

FIG. 15A is a cross-sectional view of a display unit 100B.

The display unit 100B differs from the display unit 100A mainly in thatthe display unit 100B includes the protective layer 116 and has a solidsealing structure.

Providing the protective layer 116 that covers the light-receivingdevice 110 and the light-emitting device 190 can inhibit entry ofimpurities such as water into the light-receiving device 110 and thelight-emitting device 190, thereby increasing the reliability of thelight-receiving device 110 and the light-emitting device 190.

In the region 228 in the vicinity of an end portion of the display unit100B, the insulating layer 215 and the protective layer 116 arepreferably in contact with each other through an opening in theinsulating layer 214. In particular, the inorganic insulating filmincluded in the insulating layer 215 and the inorganic insulating filmincluded in the protective layer 116 are preferably in contact with eachother. Thus, entry of impurities from the outside into the displayportion 162 through the organic insulating film can be inhibited.Accordingly, the reliability of the display unit 100B can be increased.

FIG. 15B illustrates an example in which the protective layer 116 has athree-layer structure. In FIG. 15B, the protective layer 116 includes aninorganic insulating layer 116 a over the common electrode 115, anorganic insulating layer 116 b over the inorganic insulating layer 116a, and an inorganic insulating layer 116 c over the organic insulatinglayer 116 b.

An end portion of the inorganic insulating layer 116 a and an endportion of the inorganic insulating layer 116 c extend beyond an endportion of the organic insulating layer 116 b and are in contact witheach other. The inorganic insulating layer 116 a is in contact with theinsulating layer 215 (inorganic insulating layer) through the opening inthe insulating layer 214 (organic insulating layer). Accordingly, thelight-receiving device 110 and the light-emitting device 190 can besurrounded by the insulating layer 215 and the protective layer 116,whereby the reliability of the light-receiving device 110 and thelight-emitting device 190 can be increased.

As described above, the protective layer 116 may have a stacked-layerstructure of an organic insulating film and an inorganic insulatingfilm. In that case, an end portion of the inorganic insulating filmpreferably extends beyond an end portion of the organic insulating film.

In the display unit 100B, the protective layer 116 and the substrate 152are attached to each other with the adhesive layer 142. The adhesivelayer 142 is provided to overlap with the light-receiving device 110 andthe light-emitting device 190; that is, the display unit 100B employs asolid sealing structure.

[Display Unit 100C]

FIG. 16 and FIG. 17A are cross-sectional views of a display unit 100C. Aperspective view of the display unit 100C is similar to that of thedisplay unit 100A (FIG. 13 ). FIG. 16 illustrates an example of crosssections of part of a region including the FPC 172, part of the circuit164, and part of the display portion 162 in the display unit 100C. FIG.17A illustrates an example of a cross section of part of the displayportion 162 in the display unit 100C. FIG. 16 specifically shows anexample of a cross section of a region including the light-receivingdevice 110 and the light-emitting device 190R emitting red light in thedisplay portion 162. FIG. 17A specifically shows an example of a crosssection of a region including the light-emitting device 190G emittinggreen light and the light-emitting device 190B emitting blue light inthe display portion 162.

The display unit 100C illustrated in FIG. 16 and FIG. 17A includes atransistor 203, a transistor 207, a transistor 208, a transistor 209, atransistor 210, the light-emitting device 190R, the light-emittingdevice 190G, the light-emitting device 190B, the light-receiving device110, and the like between the substrate 153 and the substrate 154.

The resin layer 159 and the common electrode 115 adhere to each otherwith the adhesive layer 142 provided therebetween, and the display unit100C employs a solid sealing structure.

The substrate 153 and the insulating layer 212 are attached to eachother with the adhesive layer 155. The substrate 154 and an insulatinglayer 157 are attached to each other with an adhesive layer 156.

To fabricate the display unit 100C, first, a first formation substrateprovided with the insulating layer 212, the transistors, thelight-receiving device 110, the light-emitting devices, and the like anda second formation substrate provided with the insulating layer 157, theresin layer 159, the light-blocking layer 158, and the like are attachedto each other with the adhesive layer 142. Then, the substrate 153 isattached to a surface exposed by separation of the first formationsubstrate, and the substrate 154 is attached to a surface exposed byseparation of the second formation substrate, whereby the componentsformed over the first formation substrate and the second formationsubstrate are transferred to the substrate 153 and the substrate 154.The substrate 153 and the substrate 154 are preferably flexible.Accordingly, the display unit 100C can be highly flexible.

The inorganic insulating film that can be used as the insulating layer211, the insulating layer 213, and the insulating layer 215 can be usedas the insulating layer 212 and the insulating layer 157.

The light-emitting device 190R has a stacked-layer structure in whichthe pixel electrode 191R, the common layer 112, the light-emitting layer193R, the common layer 114, and the common electrode 115 are stacked inthis order from an insulating layer 214 b side. The pixel electrode 191Ris connected to a conductive layer 169R through an opening provided inthe insulating layer 214 b. The conductive layer 169R is connected tothe conductive layer 222 b included in the transistor 208 through anopening provided in an insulating layer 214 a. The conductive layer 222b is connected to a low-resistance region 231 n through an openingprovided in the insulating layer 215. That is, the pixel electrode 191Ris electrically connected to the transistor 208. The transistor 208 hasa function of controlling the driving of the light-emitting device 190R.

Similarly, the light-emitting device 190G has a stacked-layer structurein which the pixel electrode 191G, the common layer 112, thelight-emitting layer 193G, the common layer 114, and the commonelectrode 115 are stacked in this order from the insulating layer 214 bside. The pixel electrode 191G is electrically connected to thelow-resistance region 231 n of the transistor 209 through a conductivelayer 169G and the conductive layer 222 b of the transistor 209. Thatis, the pixel electrode 191G is electrically connected to the transistor209. The transistor 209 has a function of controlling the driving of thelight-emitting device 190G.

The light-emitting device 190B has a stacked-layer structure in whichthe pixel electrode 191B, the common layer 112, the light-emitting layer193B, the common layer 114, and the common electrode 115 are stacked inthis order from the insulating layer 214 b side. The pixel electrode191B is electrically connected to the low-resistance region 231 n of thetransistor 210 through a conductive layer 169B and the conductive layer222 b of the transistor 210. That is, the pixel electrode 191B iselectrically connected to the transistor 210. The transistor 210 has afunction of controlling the driving of the light-emitting device 190B.

The light-receiving device 110 has a stacked-layer structure in whichthe pixel electrode 181, the common layer 112, the active layer 183, thecommon layer 114, and the common electrode 115 are stacked in this orderfrom the insulating layer 214 b side. The pixel electrode 181 iselectrically connected to the low-resistance region 231 n of thetransistor 207 through a conductive layer 168 and the conductive layer222 b of the transistor 207. That is, the pixel electrode 181 iselectrically connected to the transistor 207.

End portions of the pixel electrodes 181, 191R, 191G, and 191B arecovered with the partition 216. The pixel electrodes 181, 191R, 191G,and 191B contain a material that reflects visible light, and the commonelectrode 115 contains a material that transmits visible light.

Light from the light-emitting devices 190R, 190G, and 190B is emittedtoward the substrate 154. Light enters the light-receiving device 110through the substrate 154 and the adhesive layer 142. For the substrate154, a material having a high visible-light-transmitting property ispreferably used.

The pixel electrode 181 and the pixel electrode 191 can be formed usingthe same material in the same step. The common layer 112, the commonlayer 114, and the common electrode 115 are shared by thelight-receiving device 110 and the light-emitting devices 190R, 190G,and 190B. The light-receiving device 110 and the light-emitting devicesof different colors can have common components except the active layer183 and the light-emitting layer. Thus, the light-receiving device 110can be incorporated into the display unit 100C without a significantincrease in the number of manufacturing steps.

The resin layer 159 and the light-blocking layer 158 are provided on asurface of the insulating layer 157 on the substrate 153 side. The resinlayer 159 is provided at the positions overlapping with thelight-emitting devices 190R, 190G, and 190B and is not provided at theposition overlapping with the light-receiving device 110. Thelight-blocking layer 158 is provided to cover the surface of theinsulating layer 157 on the substrate 153 side, a side surface of theresin layer 159, and a surface of the resin layer 159 on the substrate153 side. The light-blocking layer 158 has openings at the positionoverlapping with the light-receiving device 110 and at the positionsoverlapping with the light-emitting devices 190R, 190G, and 190B.Providing the light-blocking layer 158 can control the range where thelight-receiving device 110 senses light. Moreover, providing thelight-blocking layer 158 can inhibit direct entry of light into thelight-receiving device 110 from the light-emitting devices 190R, 190G,and 190B without via an object. Hence, a sensor with less noise and highsensitivity can be obtained. Since the resin layer 159 is provided, thedistance from the light-blocking layer 158 to the light-emitting deviceof each color is shorter than the distance from the light-blocking layer158 to the light-receiving device 110. Accordingly, viewing angledependence of display can be reduced while noise of the sensor isreduced. Thus, both the display quality and imaging quality can beincreased.

The structures of the partition 216, the light-blocking layer 219 a, andthe spacer 219 b in the display unit 100C are the same as those in thedisplay unit 10K (see FIG. 7B and FIG. 8A).

In FIG. 16 , the partition 216 has an opening between thelight-receiving device 110 and the light-emitting device 190R. Thelight-blocking layer 219 a is provided so as to fill the opening. Thelight-blocking layer 219 a is positioned between the light-receivingdevice 110 and the light-emitting device 190R. The light-blocking layer219 a absorbs light emitted from the light-emitting device 190R. Thus,stray light entering the light-receiving device 110 can be reduced.

The spacer 219 b is positioned between the light-emitting device 190Gand the light-emitting device 190B. The top surface of the spacer 219 bis preferably closer to the light-blocking layer 158 than the topsurface of the light-blocking layer 219 a is. For example, the sum ofthe height (thickness) of the partition 216 and the height (thickness)the spacer 219 b is preferably larger than the height (thickness) of thelight-blocking layer 219 a. Thus, the inside of the light-blocking layer219 a can be easily filled with the adhesive layer 142. As illustratedin FIG. 17A, the light-blocking layer 158 may be in contact with thecommon electrode 115 (or the protective layer) in a portion where thespacer 219 b and the light-blocking layer 158 overlap with each other.

The connection portion 204 is provided in a region of the substrate 153where the substrate 154 does not overlap. In the connection portion 204,the wiring 165 is electrically connected to the FPC 172 through aconductive layer 167, the conductive layer 166, and the connection layer242. The conductive layer 167 can be obtained by processing the sameconductive film as the conductive layer 168. On the top surface of theconnection portion 204, the conductive layer 166 obtained by processingthe same conductive film as the pixel electrode 181 is exposed. Thus,the connection portion 204 and the FPC 172 can be electrically connectedto each other through the connection layer 242.

Each of the transistors 207, 208, 209, and 210 includes the conductivelayer 221 functioning as a gate, the insulating layer 211 functioning asa gate insulating layer, a semiconductor layer including a channelformation region 231 i and a pair of low-resistance regions 231 n, theconductive layer 222 a connected to one of the low-resistance regions231 n, the conductive layer 222 b connected to the other low-resistanceregion 231 n, an insulating layer 225 functioning as a gate insulatinglayer, the conductive layer 223 functioning as a gate, and theinsulating layer 215 covering the conductive layer 223. The insulatinglayer 211 is positioned between the conductive layer 221 and the channelformation region 231 i. The insulating layer 225 is positioned betweenthe conductive layer 223 and the channel formation region 231 i.

The conductive layer 222 a and the conductive layer 222 b are connectedto the corresponding low-resistance regions 231 n through openingsprovided in the insulating layer 215. One of the conductive layers 222 aand 222 b serves as a source, and the other serves as a drain.

In FIG. 16 , the insulating layer 225 overlaps with the channelformation region 231 i of the semiconductor layer 231 and does notoverlap with the low-resistance regions 231 n. The structure illustratedin FIG. 16 is obtained by processing the insulating layer 225 with theconductive layer 223 as a mask, for example. In FIG. 16 , the insulatinglayer 215 is provided to cover the insulating layer 225 and theconductive layer 223, and the conductive layer 222 a and the conductivelayer 222 b are connected to the low-resistance regions 231 n throughthe openings in the insulating layer 215. Furthermore, an insulatinglayer that covers the transistor may be provided over the conductivelayer 222 a and the conductive layer 222 b.

FIG. 17B illustrates an example of the transistor 202 in which theinsulating layer 225 covers atop surface and aside surface of thesemiconductor layer. The conductive layer 222 a and the conductive layer222 b are connected to the corresponding low-resistance regions 231 nthrough openings provided in the insulating layer 225 and the insulatinglayer 215.

As described above, the display unit of this embodiment includes alight-receiving device and a light-emitting device in a display portion,and the display portion has both a function of displaying an image and afunction of sensing light. Thus, the size and weight of an electronicdevice can be reduced as compared to the case where a sensor is providedoutside a display portion or outside a display unit. Moreover, anelectronic device having more functions can be obtained by a combinationof the display unit of this embodiment and a sensor provided outside thedisplay portion or outside the display unit.

In the light-receiving device, at least one of the layers providedbetween a pair of electrodes can be shared with the light-emittingdevice (EL device). For example, all the layers in the light-receivingdevice except the active layer can be common to the layers in thelight-emitting device (EL device). In other words, with only theaddition of the step of forming the active layer to the manufacturingprocess of the light-emitting device, the light-emitting device and thelight-receiving device can be formed over one substrate. In thelight-receiving device and the light-emitting device, their pixelelectrodes can be formed using the same material in the same step, andtheir common electrodes can be formed using the same material in thesame step. When a circuit electrically connected to the light-receivingdevice and a circuit electrically connected to the light-emitting deviceare formed using the same material in the same process, themanufacturing process of the display unit can be simplified. In such amanner, a display unit that incorporates a light-receiving device and ishighly convenient can be manufactured without complicated steps.

The display unit of this embodiment includes a light-emitting device inwhich holes are easily injected into the light-emitting layer andelectrons are less likely to be injected into the light-emitting layer.Such a structure inhibits initial decay of the light-emitting device andachieves an extremely long driving lifetime. Thus, the reliability ofthe light-emitting device or even the reliability of the display unitcan be increased.

In the display unit of this embodiment, on a surface where thelight-blocking layer is formed, a component is provided so that thedistance from the light-blocking layer to the light-receiving device islong and the distance from the light-blocking layer to thelight-emitting device is short. Accordingly, noise of the sensor can bereduced, the imaging resolution can be increased, and viewing angledependence of display can be reduced. Thus, both the display quality andimaging quality of the display unit can be increased.

This embodiment can be combined with the other embodiments asappropriate. In this specification, in the case where a plurality ofstructure examples are shown in one embodiment, the structure examplescan be combined as appropriate.

Embodiment 2

In this embodiment, a light-emitting device that can be used in thedisplay unit of one embodiment of the present invention will bedescribed with reference to FIGS. 18A to 18D.

A light-emitting device illustrated in FIG. 18A includes an anode 101,an EL layer 103, and a cathode 102. The light-emitting device in FIG.18A has a single structure in which one EL layer is positioned between apair of electrodes. The EL layer 103 includes a hole-injection layer121, a hole-transport layer 122, a light-emitting layer 123, anelectron-transport layer 124, and an electron-injection layer 125 fromthe anode 101 side. Although not illustrated in FIGS. 18A to 18D, thelight-emitting device may include an optical adjustment layer.

The anode 101, the cathode 102, the hole-injection layer 121, thehole-transport layer 122, the light-emitting layer 123, theelectron-transport layer 124, and the electron-injection layer 125 mayeach have a single-layer structure or a stacked-layer structure.

A light-emitting device illustrated in FIG. 18B includes the anode 101,an EL layer 103 a, a charge generation layer 104, an EL layer 103 b, andthe cathode 102. The light-emitting device in FIG. 18B has a tandemstructure including the charge generation layer 104 between the two ELlayers.

Each of the EL layers in the tandem light-emitting device can have astructure similar to that of an EL layer included in any of singlelight-emitting devices illustrated in FIGS. 18A, 18C, and 18D, forexample.

The charge generation layer 104 has a function of injecting electronsinto one of the EL layers 103 a and 103 b and injecting holes into theother of the EL layers when voltage is applied between the anode 101 andthe cathode 102. Thus, in FIG. 18B, when voltage is applied so that thepotential of the anode 101 becomes higher than that of the cathode 102,the charge generation layer 104 injects electrons into the EL layer 103a and injects holes into the EL layer 103 b.

Varying emission colors of EL layers in a tandem light-emitting devicemakes it possible for the light-emitting device as a whole to obtainlight emission of an intended color. For example, in a light-emittingdevice including two EL layers, when red light and green light areemitted from one of the EL layers and blue light is emitted from theother EL layer, the light-emitting device as a whole can emit whilelight. As another example, in a light-emitting device including three ELlayers, when blue light is emitted from the first EL layer, green lightis emitted from the second EL layer, and red light is emitted from thethird EL layer, the light-emitting device as a whole can emit whilelight. As another example, in a light-emitting device including three ELlayers, when blue light is emitted from the first EL layer, yellow,yellow green, or green light and red light are emitted from the secondEL layer over the first EL layer, and blue light is emitted from thethird EL layer over the second EL layer, the light-emitting device as awhole can emit while light. As another example, in a light-emittingdevice including four EL layers, when blue light is emitted from thefirst EL layer, yellow, yellow green, or green light is emitted from oneof the second EL layer and the third EL layer over the first EL layer,red light is emitted from the other of the second EL layer and the thirdEL layer, and blue light is emitted from the fourth EL layer over thesecond EL layer and the third EL layer, the light-emitting device as awhole can emit while light.

The hole-transport layer 122 included in the light-emitting devicesillustrated in FIGS. 18C and 18D has a two-layer structure of ahole-transport layer 122 a closer to the hole-injection layer 121 and ahole-transport layer 122 b closer to the light-emitting layer 123.

The electron-transport layer 124 included in the light-emitting devicein FIG. 18D has a two-layer structure of an electron-transport layer 124a closer to the light-emitting layer 123 and an electron-transport layer124 b closer to the electron-injection layer 125.

At least one of the hole-injection layer, the hole-transport layer, theelectron-transport layer, and the electron-injection layer included inthe light-emitting device of this embodiment can be a layer common tothe light-receiving device. Consequently, the number of manufacturingsteps can be reduced as compared to the case where the light-emittingdevice and the light-receiving device are separately formed, and thelight-emitting device and the light-receiving device can be formed onthe same plane.

For example, in the light-emitting device of this embodiment, thehole-injection layer, the hole-transport layer, the electron-transportlayer, and the electron-injection layer can all be layers common to thelight-receiving device. Thus, the light-emitting device and thelight-receiving device can be formed on the same plane only by separateformation of the light-emitting layer of the light-emitting device andthe active layer of the light-receiving device.

Materials that can be used in the light-emitting device will bedescribed below.

<Electrode>

For the pair of electrodes of the light-emitting device, a metal, analloy, an electrically conductive compound, a mixture thereof, and thelike can be used as appropriate. Specifically, an In—Sn oxide (alsoreferred to as ITO), an In—Si—Sn oxide (also referred to as ITSO), anIn—Zn oxide, or an In—W—Zn oxide can be used. In addition, it ispossible to use a metal such as aluminum (Al), titanium (Ti), chromium(Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu),gallium (Ga), zinc (Zn), indium (In), tin (Sn), molybdenum (Mo),tantalum (Ta), tungsten (W), palladium (Pd), gold (Au), platinum (Pt),silver (Ag), yttrium (Y), or neodymium (Nd) or an alloy containing anappropriate combination of any of these metals. It is also possible touse a Group 1 element or a Group 2 element in the periodic table, whichis not described above (e.g., lithium (Li), cesium (Cs), calcium (Ca),or strontium (Sr)), a rare earth metal such as europium (Eu) orytterbium (Yb), an alloy containing an appropriate combination of any ofthese elements, graphene, or the like.

To fabricate a light-emitting device having a microcavity structure, areflective electrode and a transflective electrode are used. Asingle-layer structure or a stacked-layer structure using one or morekinds of desired conductive materials can be employed. The electrodescan be formed by a sputtering method or a vacuum evaporation method.

<Hole-Injection Layer>

The hole-injection layer 121 preferably contains a first compound and asecond compound.

The first compound is an electron-accepting material (an acceptormaterial) and has a property of accepting electrons from the secondcompound.

The second compound is a hole-transport material. The hole-transportmaterial has a hole-transport property higher than an electron-transportproperty.

The highest occupied molecular orbital level (HOMO level) of the secondcompound is preferably relatively low (deep). Specifically, the HOMOlevel of the second compound is preferably higher than or equal to −5.7eV and lower than or equal to −5.4 eV. A relatively low HOMO level ofthe second compound is preferable because hole injection into thehole-transport layer 122 can be easily performed.

As the first compound, an organic compound having anelectron-withdrawing group (particularly a cyano group or a halogengroup such as a fluoro group) can be used.

As the first compound, an organic acceptor such as a quinodimethanederivative, a chloranil derivative, and a hexaazatriphenylene derivativecan be used, for example. Specific examples include7,7,8,8-tetracyano-2,3,5,6-tetrafluoroquinodimethane (abbreviation:F4-TCNQ), chloranil,2,3,6,7,10,11-hexacyano-1,4,5,8,9,12-hexaazatriphenylene (abbreviation:HAT-CN), 1,3,4,5,7,8-hexafluorotetracyano-naphthoquinodimethane(abbreviation: F6-TCNNQ), and2-(7-dicyanomethylene-1,3,4,5,6,8,9,10-octafluoro-7H-pyren-2-ylidene)malononitrile.A compound in which electron-withdrawing groups are bonded to acondensed aromatic ring having a plurality of heteroatoms, such asHAT-CN, is preferred because it is thermally stable. A [3]radialenederivative having an electron-withdrawing group (in particular, a cyanogroup or a halogen group such as a fluoro group) has a very highelectron-accepting property and thus is preferred. Specific examples ofa [3]radialene derivative having an electron-withdrawing group includeα,α,α″-1,2,3-cyclopropanetriylidenetris[4-cyano-2,3,5,6-tetrafluorobenzeneacetonitrile],α,α,α″-1,2,3-cyclopropanetriylidenetris[2,6-dichloro-3,5-difluoro-4-(trifluoromethyl)benzeneacetonitrile],andα,α,α″-1,2,3-cyclopropanetriylidenetris[2,3,4,5,6-pentafluorobenzeneacetonitrile].

The second compound preferably has a hole-transport skeleton. Acarbazole skeleton, a dibenzofuran skeleton, a dibenzothiopheneskeleton, and an anthracene skeleton, with which the HOMO level of thehole-transport material does not become too high (shallow), arepreferably used as the hole-transport skeleton.

The second compound preferably has at least one of a carbazole skeleton,a dibenzofuran skeleton, a dibenzothiophene skeleton, and an anthraceneskeleton. The second compound may be an aromatic amine having asubstituent that includes a dibenzofuran ring or a dibenzothiophenering, an aromatic monoamine that includes a naphthalene ring, or anaromatic monoamine in which a 9-fluorenyl group is bonded to nitrogen ofamine through an arylene group.

The second organic compound having an N,N-bis(4-biphenyl)amino group ispreferred because a light-emitting device having a long lifetime can befabricated.

Examples of the second compound includeN-(4-biphenyl)-6,N-diphenylbenzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BnfABP),N,N-bis(4-biphenyl)-6-phenylbenzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BBABnf),4,4′-bis(6-phenylbenzo[b]naphtho[1,2-d]furan-8-yl)-4″-phenyltriphenylamine(abbreviation: BnfBB1BP),N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-6-amine (abbreviation:BBABnf(6)), N,N-bis(4-biphenyl)benzo[b]naphtho[1,2-d]furan-8-amine(abbreviation: BBABnf(8)),N,N-bis(4-biphenyl)benzo[b]naphtho[2,3-d]furan-4-amine (abbreviation:BBABnf(II)(4)), N,N-bis[4-(dibenzofuran-4-yl)phenyl]-4-amino-p-terphenyl(abbreviation: DBfBB1TP),N-[4-(dibenzothiophen-4-yl)phenyl]-N-phenyl-4-biphenylamine(abbreviation: ThBA1BP), 4-(2-naphthyl)-4′,4″-diphenyltriphenylamine(abbreviation: BBAβNB),4-[4-(2-naphthyl)phenyl]-4′,4″-diphenyltriphenylamine (abbreviation:BBAβNBi), 4,4′-diphenyl-4″-(6;1′-binaphthyl-2-yl)triphenylamine(abbreviation: BBAαNβNB),4,4′-diphenyl-4″-(7;1′-binaphthyl-2-yl)triphenylamine (abbreviation:BBAαNβNB-03), 4,4′-diphenyl-4″-(7-phenyl)naphthyl-2-yltriphenylamine(abbreviation: BBAPβNB-03),4,4′-diphenyl-4″-(6;2′-binaphthyl-2-yl)triphenylamine (abbreviation:BBA(βN2)B), 4,4′-diphenyl-4″-(7;2′-binaphthyl-2-yl)triphenylamine(abbreviation: BBA(βN2)B-03),4,4′-diphenyl-4″-(4;2′-binaphthyl-1-yl)triphenylamine (abbreviation:BBAβNαNB), 4,4′-diphenyl-4″-(5;2′-binaphthyl-1-yl)triphenylamine(abbreviation: BBAβNαNB-02),4-(4-biphenylyl)-4′-(2-naphthyl)-4″-phenyltriphenylamine (abbreviation:TPBiAβNB),4-(3-biphenylyl)-4′-[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine(abbreviation: mTPBiAβNBi),4-(4-biphenylyl)-4′-[4-(2-naphthyl)phenyl]-4″-phenyltriphenylamine(abbreviation: TPBiAβNBi), 4-phenyl-4′-(1-naphthyl)-triphenylamine(abbreviation: αNBA1BP), 4,4′-bis(1-naphthyl)triphenylamine(abbreviation: αNBB1BP),4,4′-diphenyl-4″-[4′-(carbazol-9-yl)biphenyl-4-yl]triphenylamine(abbreviation: YGTBi1BP),4′-[4-(3-phenyl-9H-carbazol-9-yl)phenyl]tris(1,1′-biphenyl-4-yl)amine(abbreviation: YGTBi1BP-02),4-[4′-(carbazol-9-yl)biphenyl-4-yl]-4′-(2-naphthyl)-4″-phenyltriphenylamine(abbreviation: YGTBiβNB),N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-N-[4-(1-naphthyl)phenyl]-9,9′-spirobi[9H-fluoren]-2-amine(abbreviation: PCBNBSF),N,N-bis(4-biphenylyl)-9,9′-spirobi[9H-fluoren]-2-amine (abbreviation:BBASF), N,N-bis(1,1′-biphenyl-4-yl)-9,9′-spirobi[9H-fluoren]-4-amine(abbreviation: BBASF(4)),N-(1,1′-biphenyl-2-yl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9,9′-spirobi[9H-fluoren]-4-amine(abbreviation: oFBiSF),N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)dibenzofuran-4-amine(abbreviation: FrBiF),N-[4-(1-naphthyl)phenyl]-N-[3-(6-phenyldibenzofuran-4-yl)phenyl]-1-naphthylamine(abbreviation: mPDBfBNBN),4-phenyl-4′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation: BPAFLP),4-phenyl-3′-(9-phenylfluoren-9-yl)triphenylamine (abbreviation:mBPAFLP), 4-phenyl-4′-[4-(9-phenylfluoren-9-yl)phenyl]triphenylamine(abbreviation: BPAFLBi),4-phenyl-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine (abbreviation:PCBA1BP), 4,4′-diphenyl-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBBi1BP),4-(1-naphthyl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBANB),4,4′-di(1-naphthyl)-4″-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBNBB),N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]spiro-9,9′-bifluoren-2-amine(abbreviation: PCBASF),N-(1,1′-biphenyl-4-yl)-9,9-dimethyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]-9H-fluoren-2-amine(abbreviation: PCBBiF),3,3′-(naphthalen-1,4-diyl)bis(9-phenyl-9H-carbazole) (abbreviation:PCzN2), and4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-fluoren-9-yl)triphenylamine(abbreviation: FLPAPA).

<Hole-Transport Layer>

The hole-transport layer 122 transports holes injected by thehole-injection layer 121, to the light-emitting layer 123.

The hole-transport layer 122 preferably contains a third compound.

The third compound is a hole-transport material. As the hole-transportmaterial, a hole-transport material that can be used as the secondcompound can be used.

The HOMO level of the third compound is preferably lower than or equalto that of the second compound. The difference in the HOMO level betweenthe third compound and the second compound is preferably 0.2 eV or less.

The second compound and the third compound each preferably include atleast one of a carbazole skeleton, a dibenzofuran skeleton, adibenzothiophene skeleton, and an anthracene skeleton.

It is preferable that the second compound and the third compound havethe same hole-transport skeleton (especially a dibenzofuran skeleton),in which case holes can be injected smoothly.

It is further preferable that the second compound and the third compoundare the same compound, in which case holes can be injected smoothly.

In the case where the hole-transport layer 122 has a stacked-layerstructure, each of the layers included in the hole-transport layer 122transports holes to the light-emitting layer 123.

The hole-transport layer 122 a in FIGS. 18C and 18D can have a structuresimilar to that of the hole-transport layer 122 in FIG. 18A.

The hole-transport layer 122 b in FIGS. 18C and 18D (i.e., the layer inthe hole-transport layer 122 that is located closest to thelight-emitting layer 123) preferably has a function of anelectron-blocking layer.

The hole-transport layer 122 b preferably contains a fourth compound.

The fourth compound is a hole-transport material. As the hole-transportmaterial, a hole-transport material that can be used as the secondcompound can be used.

The HOMO level of the fourth compound is preferably lower than that ofthe third compound. The difference in the HOMO level between the fourthcompound and the third compound is preferably 0.2 eV or less.

The second compound, the third compound, and the fourth compound eachpreferably include at least one of a carbazole skeleton, a dibenzofuranskeleton, a dibenzothiophene skeleton, and an anthracene skeleton.

It is preferable that the second compound, the third compound, and thefourth compound have the same hole-transport skeleton (especially adibenzofuran skeleton), in which case holes can be injected smoothly.

When the second compound and the third compound (and also the fourthcompound) have a small difference in the HOMO level or have ahole-transport skeleton (preferably the same hole-transport skeleton) asdescribed above, holes are smoothly injected into the hole-injectionlayer and the hole transport layer, thereby preventing an increase indriving voltage and deficiency of holes in the light-emitting layer 123.

<Light-Emitting Layer>

The light-emitting layer contains a light-emitting substance. Thelight-emitting layer can contain one or more kinds of light-emittingsubstances. As the light-emitting substance, a substance whose emissioncolor is blue, violet, bluish violet, green, yellowish green, yellow,orange, red, or the like is appropriately used. Alternatively, asubstance that emits infrared light can be used as the light-emittingsubstance.

The light-emitting layer may contain one or more kinds of organiccompounds (e.g., a host material or an assist material) in addition tothe light-emitting substance (guest material). As one or more kinds oforganic compounds, one or both of the hole-transport material and theelectron-transport material described in this embodiment can be used.Moreover, as one or more kinds of organic compounds, a bipolar materialmay be used.

There is no particular limitation on the light-emitting substance thatcan be used for the light-emitting layer, and it is possible to use alight-emitting substance that converts singlet excitation energy intolight in the visible light range or the near-infrared region or alight-emitting substance that converts triplet excitation energy intolight in the visible light range or the near-infrared region.

Examples of a light-emitting substance that converts singlet excitationenergy into light are substances that exhibit fluorescence (fluorescentmaterials) such as a pyrene derivative, an anthracene derivative, atriphenylene derivative, a fluorene derivative, a carbazole derivative,a dibenzothiophene derivative, a dibenzofuran derivative, adibenzoquinoxaline derivative, a quinoxaline derivative, a pyridinederivative, a pyrimidine derivative, a phenanthrene derivative, and anaphthalene derivative. A pyrene derivative is particularly preferablebecause it has a high emission quantum yield. Specific examples of thepyrene derivative includeN,N′-bis(3-methylphenyl)-N,N′-bis[3-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6mMemFLPAPm),N,N′-diphenyl-N,N′-bis[4-(9-phenyl-9H-fluoren-9-yl)phenyl]pyrene-1,6-diamine(abbreviation: 1,6FLPAPrn),N,N′-bis(dibenzofuran-2-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6FrAPrn),N,N′-bis(dibenzothiophen-2-yl)-N,N′-diphenylpyrene-1,6-diamine(abbreviation: 1,6ThAPrn),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-6-amine](abbreviation: 1,6BnfAPrn),N,N′-(pyrene-1,6-diyl)bis[(N-phenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation:1,6BnfAPrn-02), andN,N′-(pyrene-1,6-diyl)bis[(6,N-diphenylbenzo[b]naphtho[1,2-d]furan)-8-amine](abbreviation: 1,6BnfAPrn-03). Condensed aromatic diamine compoundstypified by pyrenediamine compounds such as 1,6FLPAPrn, 1,6mMemFLPAPm,and 1,6BnfAPm-03 are particularly preferred because of their highhole-trapping properties, high emission efficiency, and highreliability.

In addition, it is possible to use5,6-bis[4-(10-phenyl-9-anthryl)phenyl]-2,2′-bipyridine (abbreviation:PAP2BPy), 5,6-bis[4′-(10-phenyl-9-anthryl)biphenyl-4-yl]-2,2′-bipyridine(abbreviation: PAPP2BPy),N,N′-bis[4-(9H-carbazol-9-yl)phenyl]-N,N′-diphenylstilbene-4,4′-diamine(abbreviation: YGA2S),4-(9H-carbazol-9-yl)-4′-(10-phenyl-9-anthryl)triphenylamine(abbreviation: YGAPA),4-(9H-carbazol-9-yl)-4′-(9,10-diphenyl-2-anthryl)triphenylamine(abbreviation: 2YGAPPA),N,9-diphenyl-N-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: PCAPA),4-(10-phenyl-9-anthryl)-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPA),4-[4-(10-phenyl-9-anthryl)phenyl]-4′-(9-phenyl-9H-carbazol-3-yl)triphenylamine(abbreviation: PCBAPBA), perylene, 2,5,8,11-tetra(tert-butyl)perylene(abbreviation: TBP),N,N″-(2-tert-butylanthracene-9,10-diyldi-4,1-phenylene)bis[N,N′,N′-triphenyl-1,4-phenylenediamine](abbreviation: DPABPA),N,9-diphenyl-N-[4-(9,10-diphenyl-2-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: 2PCAPPA),N-[4-(9,10-diphenyl-2-anthryl)phenyl]-N,N′,N′-triphenyl-1,4-phenylenediamine(abbreviation: 2DPAPPA),3,10-bis[N-(9-phenyl-9H-carbazole-2-yl)-N-phenylamino]naphtho[2,3-b;6,7-b′]bisbenzofuran(abbreviation: 3,10PCA2Nbf(IV)-02),3,10-bis[N-(dibenzofuran-3-yl)-N-phenylamino]naphtho[2,3-b;6,7-b′]bisbenzofuran(abbreviation: 3,10FrA2Nbf(IV)-02), and the like.

Examples of a light-emitting substance that converts triplet excitationenergy into light include a substance that exhibits phosphorescence (aphosphorescent material) and a thermally activated delayed fluorescent(TADF) material that exhibits thermally activated delayed fluorescence.

Examples of a phosphorescent material include an organometallic complex(particularly an iridium complex) having a 4H-triazole skeleton, a1H-triazole skeleton, an imidazole skeleton, a pyrimidine skeleton, apyrazine skeleton, or a pyridine skeleton; an organometallic complex(particularly an iridium complex) having a phenylpyridine skeletonincluding an electron-withdrawing group as a ligand; a platinum complex;and a rare earth metal complex

As examples of a phosphorescent material which emits blue or green lightand whose emission spectrum has a peak wavelength at greater than orequal to 450 nm and less than or equal to 570 nm, the followingsubstances can be given.

Examples include organometallic complexes having a 4H-triazole skeleton,such astris{2-[5-(2-methylphenyl)-4-(2,6-dimethylphenyl)-4H-1,2,4-triazol-3-yl-κN²]phenyl-C}iridium(III)(abbreviation: [Ir(mpptz-dmp)₃]),tris(5-methyl-3,4-diphenyl-4H-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Mptz)₃]),tris[4-(3-biphenyl)-5-isopropyl-3-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPrptz-3b)₃]), andtris[3-(5-biphenyl)-5-isopropyl-4-phenyl-4H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(iPr5btz)₃]); organometallic complexes having a1H-triazole skeleton, such astris[3-methyl-1-(2-methylphenyl)-5-phenyl-H-1,2,4-triazolato]iridium(III)(abbreviation: [Ir(Mptz1-mp)₃]) andtris(1-methyl-5-phenyl-3-propyl-TH-1,2,4-triazolato)iridium(III)(abbreviation: [Ir(Prptz1-Me)₃]); organometallic complexes having animidazole skeleton, such asfac-tris[1-(2,6-diisopropylphenyl)-2-phenyl-H-imidazole]iridium(III)(abbreviation: [Ir(iPrpmi)₃]) andtris[3-(2,6-dimethylphenyl)-7-methylimidazo[1,2-f]phenanthridinato]iridium(III)(abbreviation: [Ir(dmpimpt-Me)₃]); and organometallic complexes in whicha phenylpyridine derivative having an electron-withdrawing group is aligand, such asbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)tetrakis(1-pyrazolyl)borate (abbreviation: FIr6),bis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III) picolinate(abbreviation: FIrpic),bis{2-[3′,5′-bis(trifluoromethyl)phenyl]pyridinato-N,C^(2′)}iridium(III)picolinate (abbreviation: [Ir(CF₃ppy)₂(pic)]), andbis[2-(4′,6′-difluorophenyl)pyridinato-N,C^(2′)]iridium(III)acetylacetonate (abbreviation: FIr(acac)).

As examples of a phosphorescent material which emits green or yellowlight and whose emission spectrum has a peak wavelength at greater thanor equal to 495 nm and less than or equal to 590 nm, the followingsubstances can be given.

Examples include organometallic iridium complexes having a pyrimidineskeleton, such as tris(4-methyl-6-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₃]),tris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]),(acetylacetonato)bis(6-methyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(mppm)₂(acac)]),(acetylacetonato)bis(6-tert-butyl-4-phenylpyrimidinato)iridium(III)(abbreviation: [Ir(tBuppm)₂(acac)]),(acetylacetonato)bis[6-(2-norbornyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(nbppm)₂(acac)]),(acetylacetonato)bis[5-methyl-6-(2-methylphenyl)-4-phenylpyrimidinato]iridium(III)(abbreviation: [Ir(mpmppm)₂(acac)]),(acetylacetonato)bis{4,6-dimethyl-2-[6-(2,6-dimethylphenyl)-4-pyrimidinyl-κN³]phenyl-κC}iridium(III)(abbreviation: [Ir(dmppm-dmp)₂(acac)]), and(acetylacetonato)bis(4,6-diphenylpyrimidinato)iridium(III)(abbreviation: [Ir(dppm)₂(acac)]); organometallic iridium complexeshaving a pyrazine skeleton, such as(acetylacetonato)bis(3,5-dimethyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-Me)₂(acac)]) and(acetylacetonato)bis(5-isopropyl-3-methyl-2-phenylpyrazinato)iridium(III)(abbreviation: [Ir(mppr-iPr)₂(acac)]); organometallic iridium complexeshaving a pyridine skeleton, such astris(2-phenylpyridinato-N,C²′)iridium(III) (abbreviation: [Ir(ppy)₃]),bis(2-phenylpyridinato-N,C^(2′))iridium(III) acetylacetonate(abbreviation: [Ir(ppy)₂(acac)]), bis(benzo[h]quinolinato)iridium(III)acetylacetonate (abbreviation: [Ir(bzq)₂(acac)]),tris(benzo[h]quinolinato)iridium(III) (abbreviation: [Ir(bzq)₃]),tris(2-phenylquinolinato-N,C^(2′))iridium(III) (abbreviation:[Ir(pq)₃]), bis(2-phenylquinolinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(pq)₂(acac)]),[2-(4-phenyl-2-pyridinyl-κN)phenyl-κC]bis[2-(2-pyridinyl-κN)phenyl-κC]iridium(III)(abbreviation: Ir(ppy)₂(4dppy)), andbis[2-(2-pyridinyl-κN)phenyl-κC][2-(4-methyl-5-phenyl-2-pyridinyl-N)phenyl-κC];organometallic complexes such asbis(2,4-diphenyl-1,3-oxazolato-N,C²)iridium(III) acetylacetonate(abbreviation: [Ir(dpo)₂(acac)]),bis{2-[4′-(perfluorophenyl)phenyl]pyridinato-N,C^(2′)}iridium(III)acetylacetonate (abbreviation: [Ir(p-PF-ph)₂(acac)]), andbis(2-phenylbenzothiazolato-N,C²′)iridium(III) acetylacetonate(abbreviation: [Ir(bt)₂(acac)]); and rare earth metal complexes such astris(acetylacetonato)(monophenanthroline)terbium(III) (abbreviation:[Tb(acac)₃(Phen)]).

As examples of a phosphorescent material which emits yellow or red lightand whose emission spectrum has a peak wavelength at greater than orequal to 570 nm and less than or equal to 750 nm, the followingsubstances can be given.

Examples include organometallic complexes having a pyrimidine skeleton,such as(diisobutyrylmethanato)bis[4,6-bis(3-methylphenyl)pyrimidinato]iridium(III)(abbreviation: [Ir(5mdppm)₂(dibm)]),bis[4,6-bis(3-methylphenyl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(5mdppm)₂(dpm)]),bis[4,6-di(naphthalen-1-yl)pyrimidinato](dipivaloylmethanato)iridium(III)(abbreviation: [Ir(d1npm)₂(dpm)]), andtris(4-t-butyl-6-phenylpyrimidinato)iridium(III) (abbreviation:[Ir(tBuppm)₃]); organometallic complexes having a pyrazine skeleton,such as (acetylacetonato)bis(2,3,5-triphenylpyrazinato)iridium(III)(abbreviation: [Ir(tppr)₂(acac)]),bis(2,3,5-triphenylpyrazinato)(dipivaloylmethanato)iridium(III)(abbreviation: [Ir(tppr)₂(dpm)]),bis{4,6-dimethyl-2-[3-(3,5-dimethylphenyl)-5-phenyl-2-pyrazinyl-κN]phenyl-κC}(2,6-dimethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-P)₂(dibm)]),bis{4,6-dimethyl-2-[5-(4-cyano-2,6-dimethylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-dmCP)₂(dpm)]),(acetylacetonato)bis[2-methyl-3-phenylquinoxalinato-N,C^(2′)]iridium(III)(abbreviation: [Ir(mpq)₂(acac)]),(acetylacetonato)bis(2,3-diphenylquinoxalinato-N,C^(2′))iridium(III)(abbreviation: [Ir(dpq)₂(acac)]),(acetylacetonato)bis[2,3-bis(4-fluorophenyl)quinoxalinato]iridium(III)(abbreviation: [Ir(Fdpq)₂(acac)]), andbis{4,6-dimethyl-2-[5-(5-cyano-2-methylphenyl)-3-(3,5-dimethylphenyl)-2-pyrazinyl-κN]phenyl-κC}(2,2,6,6-tetramethyl-3,5-heptanedionato-κ²O,O′)iridium(III)(abbreviation: [Ir(dmdppr-m5CP)₂(dpm)]); organometallic complexes havinga pyridine skeleton, such astris(1-phenylisoquinolinato-N,C^(2′))iridium(III) (abbreviation:[Ir(piq)₃]), bis(1-phenylisoquinolinato-N,C^(2′))iridium(III)acetylacetonate (abbreviation: [Ir(piq)₂(acac)]), andbis[4,6-dimethyl-2-(2-quinolinyl-κN)phenyl-κC](2,4-pentanedionato-κ²O,O′)iridium(III);platinum complexes such as2,3,7,8,12,13,17,18-octaethyl-21H,23H-porphyrin platinum(II)(abbreviation: [PtOEP]); and rare earth metal complexes such astris(1,3-diphenyl-1,3-propanedionato)(monophenanthroline)europium(III)(abbreviation: [Eu(DBM)₃(Phen)]) andtris[1-(2-thenoyl)-3,3,3-trifluoroacetonato](monophenanthroline)europium(III)(abbreviation: [Eu(TTA)₃(Phen)]).

As the organic compound (e.g., the host material or the assist material)used in the light-emitting layer, one or more kinds of substances havinga larger energy gap than the light-emitting substance can be used.

As an organic compound used in combination with a fluorescent material,it is preferable to use an organic compound that has a high energy levelin a singlet excited state and has a low energy level in a tripletexcited state.

Although partly overlapping the specific examples described above,specific examples of organic compounds will be shown from the viewpointof a preferred combination with the light-emitting substance (afluorescent material and a phosphorescent material).

Examples of organic compounds that can be used in combination with afluorescent material include condensed polycyclic aromatic compoundssuch as an anthracene derivative, a tetracene derivative, a phenanthrenederivative, a pyrene derivative, a chrysene derivative, and adibenzo[g,p]chrysene derivative.

Specific examples of organic compounds (host materials) used incombination with a fluorescent material include9-phenyl-3-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole (abbreviation:PCzPA), 3,6-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazole(abbreviation: DPCzPA), 3-[4-(1-naphthyl)-phenyl]-9-phenyl-9H-carbazole(abbreviation: PCPN), 9,10-diphenylanthracene (abbreviation: DPAnth),N,N-diphenyl-9-[4-(10-phenyl-9-anthryl)phenyl]-9H-carbazol-3-amine(abbreviation: CzA1PA), 4-(10-phenyl-9-anthryl)triphenylamine(abbreviation: DPhPA), YGAPA, PCAPA,N,9-diphenyl-N-{4-[4-(10-phenyl-9-anthryl)phenyl]phenyl}-9H-carbazol-3-amine(abbreviation: PCAPBA),N-(9,10-diphenyl-2-anthryl)-N,9-diphenyl-9H-carbazol-3-amine(abbreviation: 2PCAPA), 6,12-dimethoxy-5,11-diphenylchrysene,N,N,N′,N′,N″,N″,N′″,N′″-octaphenyldibenzo[g,p]chrysene-2,7,10,15-tetraamine(abbreviation: DBC1), 9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole(abbreviation: CzPA),7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA),6-[3-(9,10-diphenyl-2-anthryl)phenyl]-benzo[b]naphtho[1,2-d]furan(abbreviation: 2mBnfPPA),9-phenyl-10-{4-(9-phenyl-9H-fluoren-9-yl)biphenyl-4′-yl}anthracene(abbreviation: FLPPA), 9,10-bis(3,5-diphenylphenyl)anthracene(abbreviation: DPPA), 9,10-di(2-naphthyl)anthracene (abbreviation: DNA),2-tert-butyl-9,10-di(2-naphthyl)anthracene (abbreviation: t-BuDNA),9,9′-bianthryl(abbreviation: BANT),9,9′-(stilbene-3,3′-diyl)diphenanthrene (abbreviation: DPNS),9,9′-(stilbene-4,4′-diyl)diphenanthrene (abbreviation: DPNS2),1,3,5-tri(1-pyrenyl)benzene (abbreviation: TPB3),5,12-diphenyltetracene, 5,12-bis(biphenyl-2-yl)tetracene, and9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene (abbreviation:αN-βNPAnth).

As an organic compound used in combination with a phosphorescentmaterial, an organic compound having triplet excitation energy (anenergy difference between a ground state and a triplet excited state)which is higher than that of the light-emitting substance is selected.

When a plurality of organic compounds (e.g., a first host material and asecond host material (or an assist material)) are used in combinationwith the light-emitting substance so that an exciplex is formed, theplurality of organic compounds are preferably mixed with aphosphorescent material (in particular, an organometallic complex).

With such a structure, light emission can be efficiently obtained byexciplex-triplet energy transfer (ExTET), which is energy transfer froman exciplex to a light-emitting substance. Note that a combination ofthe plurality of organic compounds that easily forms an exciplex ispreferably employed, and it is particularly preferable to combine acompound that easily accepts holes (a hole-transport material) and acompound that easily accepts electrons (an electron-transport material).When a combination of materials is selected so as to form an exciplexthat exhibits light emission whose wavelength overlaps with thewavelength on a lowest-energy-side absorption band of the light-emittingsubstance, energy can be transferred smoothly and light emission can beobtained efficiently. As the hole-transport material and theelectron-transport material, specifically, any of the materialsdescribed in this embodiment can be used. With the above structure, highefficiency, low voltage driving, and a long lifetime of thelight-emitting device can be achieved at the same time.

In a combination of materials for forming an exciplex, the HOMO level ofthe electron-transport material is preferably higher than or equal tothat of the electron-transport material. In addition, the lowestunoccupied molecular orbital level (LUMO level) of the hole-transportmaterial is preferably higher than or equal to that of theelectron-transport material. The LUMO levels and the HOMO levels of thematerials can be derived from the electrochemical characteristics (thereduction potentials and the oxidation potentials) of the materials thatare measured by cyclic voltammetry (CV).

The formation of an exciplex can be confirmed, for example, by aphenomenon in which the emission spectrum of a mixed film in which thehole-transport material and the electron-transport material are mixed isshifted to the longer wavelength side than the emission spectra of eachof the materials (or has another peak on the longer wavelength side)observed by comparison of the emission spectra of the hole-transportmaterial, the electron-transport material, and the mixed film of thesematerials. Alternatively, the formation of an exciplex can be confirmedby a difference in transient response, such as a phenomenon in which thetransient photoluminescence (PL) lifetime of the mixed film has morelong-lifetime components or has a larger proportion of delayedcomponents than that of each of the materials, observed by comparison oftransient PL of the hole-transport material, the electron-transportmaterial, and the mixed film of these materials. The transient PL can berephrased as transient electroluminescence (EL). That is, the formationof an exciplex can also be confirmed by a difference in transientresponse observed by comparison of the transient EL of thehole-transport material, the electron-transport material, and the mixedfilm of the materials.

Examples of organic compounds that can be used in combination with aphosphorescent material include an aromatic amine (a compound having anaromatic amine skeleton), a carbazole derivative (a compound having acarbazole skeleton), a dibenzothiophene derivative (a thiophenederivative), a dibenzofuran derivative (a furan derivative), zinc- andaluminum-based metal complexes, an oxadiazole derivative, a triazolederivative, a benzimidazole derivative, a quinoxaline derivative, adibenzoquinoxaline derivative, a pyrimidine derivative, a triazinederivative, a pyridine derivative, a bipyridine derivative, and aphenanthroline derivative.

Specific examples of the aromatic amine, carbazole derivatives,dibenzothiophene derivatives, and dibenzofuran derivatives, which areorganic compounds having a high hole-transport property, are givenbelow.

Examples of carbazole derivatives include a bicarbazole derivative(e.g., a 3,3′-bicarbazole derivative) and an aromatic amine having acarbazolyl group.

Specific examples of bicarbazole derivatives (e.g., a 3,3′-bicarbazolederivative) include 3,3′-bis(9-phenyl-9H-carbazole) (abbreviation:PCCP), 9,9′-bis(1,1′-biphenyl-4-yl)-3,3′-bi-9H-carbazole,9,9′-bis(1,1′-biphenyl-3-yl)-3,3′-bi-9H-carbazole,9-(1,1′-biphenyl-3-yl)-9′-(1,1′-biphenyl-4-yl)-9H, 9′H-3,3′-bicarbazole(abbreviation: mBPCCBP), 9-(2-naphthyl)-9′-phenyl-9H, and9′H-3,3′-bicarbazole (abbreviation: βNCCP).

Specific examples of the aromatic amine having a carbazolyl groupinclude PCBA1BP,N-(4-biphenyl)-N-(9,9-dimethyl-9H-fluoren-2-yl)-9-phenyl-9H-carbazol-3-amine(abbreviation: PCBiF), PCBBiF, PCBBi1BP, PCBANB, PCBNBB,4-phenyldiphenyl-(9-phenyl-9H-carbazol-3-yl)amine (abbreviation:PCA1BP),N,N′-bis(9-phenylcarbazol-3-yl)-N,N′-diphenylbenzene-1,3-diamine(abbreviation: PCA2B),N,N′,N″-triphenyl-N,N′,N″-tris(9-phenylcarbazol-3-yl)benzene-1,3,5-triamine(abbreviation: PCA3B),9,9-dimethyl-N-phenyl-N-[4-(9-phenyl-9H-carbazol-3-yl)phenyl]fluoren-2-amine(abbreviation: PCBAF), PCBASF,3-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA1),3,6-bis[N-(9-phenylcarbazol-3-yl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzPCA2),3-[N-(1-naphthyl)-N-(9-phenylcarbazol-3-yl)amino]-9-phenylcarbazole(abbreviation: PCzPCN1),3-[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA1),3,6-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-9-phenylcarbazole(abbreviation: PCzDPA2),3,6-bis[N-(4-diphenylaminophenyl)-N-(1-naphthyl)amino]-9-phenylcarbazole(abbreviation: PCzTPN2),2-[N-(9-phenylcarbazol-3-yl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: PCASF),N-[4-(9H-carbazol-9-yl)phenyl]-N-(4-phenyl)phenylaniline (abbreviation:YGA1BP),N,N-bis[4-(carbazol-9-yl)phenyl]-N,N-diphenyl-9,9-dimethylfluorene-2,7-diamine(abbreviation: YGA2F), and 4,4′,4″-tris(carbazol-9-yl)triphenylamine(abbreviation: TCTA).

Other examples of the carbazole derivative include3-[4-(9-phenanthryl)-phenyl]-9-phenyl-9H-carbazole (abbreviation:PCPPn), PCPN, 1,3-bis(N-carbazolyl)benzene (abbreviation: mCP),4,4′-di(N-carbazolyl)biphenyl (abbreviation: CBP),3,6-bis(3,5-diphenylphenyl)-9-phenylcarbazole (abbreviation: CzTP),1,3,5-tris[4-(N-carbazolyl)phenyl]benzene (abbreviation: TCPB), andCzPA.

Specific examples of a thiophene derivative (a compound having athiophene skeleton) and a furan derivative (a compound having a furanskeleton) include compounds having a thiophene skeleton, such as4,4′,4″-(benzene-1,3,5-triyl)tri(dibenzothiophene) (abbreviation:DBT3P-II),2,8-diphenyl-4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]dibenzothiophene(abbreviation: DBTFLP-III), and4-[4-(9-phenyl-9H-fluoren-9-yl)phenyl]-6-phenyldibenzothiophene(abbreviation: DBTFLP-IV), and4-{3-[3-(9-phenyl-9H-fluoren-9-yl)phenyl]phenyl}dibenzofuran(abbreviation: mmDBFFLBi-II).

Specific examples of the aromatic amine include4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (abbreviation: NPB orα-NPD),N,N′-bis(3-methylphenyl)-N,N′-diphenyl-[1,1′-biphenyl]-4,4′-diamine(abbreviation: TPD),4,4′-bis[N-(spiro-9,9′-bifluoren-2-yl)-N-phenylamino]biphenyl(abbreviation: BSPB), BPAFLP, mBPAFLP,N-(9,9-dimethyl-9H-fluoren-2-yl)-N-{9,9-dimethyl-2-[N′-phenyl-N′-(9,9-dimethyl-9H-fluoren-2-yl)amino]-9H-fluoren-7-yl}phenylamine(abbreviation: DFLADFL),N-(9,9-dimethyl-2-diphenylamino-9H-fluoren-7-yl)diphenylamine(abbreviation: DPNF),2-[N-(4-diphenylaminophenyl)-N-phenylamino]spiro-9,9′-bifluorene(abbreviation: DPASF),2,7-bis[N-(4-diphenylaminophenyl)-N-phenylamino]-spiro-9,9′-bifluorene(abbreviation: DPA2SF),4,4′,4″-tris[N-(1-naphthyl)-N-phenylamino]triphenylamine (abbreviation:1′-TNATA), 4,′,4″-tris(N,N-diphenylamino)triphenylamine (abbreviation:TDATA), 4,4′,4″-tris[N-(3-methylphenyl)-N-phenylamino]triphenylamine(abbreviation: m-MTDATA),N,N′-di(p-tolyl)-N,N′-diphenyl-p-phenylenediamine (abbreviation:DTDPPA),4,4′-bis[N-(4-diphenylaminophenyl)-N-phenylamino]biphenyl(abbreviation:DPAB),4,4′-bis(N-{4-[N′-(3-methylphenyl)-N′-phenylamino]phenyl}-N-phenylamino)biphenyl(abbreviation: DNTPD), and1,3,5-tris[N-(4-diphenylaminophenyl)-N-phenylamino]benzene(abbreviation: DPA3B).

As an organic compound having a high hole-transport property, a highmolecular compound such as poly(N-vinylcarbazole) (abbreviation: PVK),poly(4-vinyltriphenylamine) (abbreviation: PVTPA),poly[N-(4-{N′-[4-(4-diphenylamino)phenyl]phenyl-N′-phenylamino}phenyl)methacrylamide](abbreviation: PTPDMA), orpoly[N,N′-bis(4-butylphenyl)-N,N-bis(phenyl)benzidine] (abbreviation:Poly-TPD) can also be used.

Specific examples of zinc- and aluminum-based metal complexes, which areorganic compounds having a high electron-transport property, includemetal complexes having a quinoline skeleton or a benzoquinolineskeleton, such as tris(8-quinolinolato)aluminum(III) (abbreviation:Alq), tris(4-methyl-8-quinolinolato)aluminum(III) (abbreviation: Almq₃),bis(10-hydroxybenzo[h]quinolinato)beryllium(II) (abbreviation: BeBq₂),bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum(III)(abbreviation: BAlq), and bis(8-quinolinolato)zinc(II) (abbreviation:Znq).

Alternatively, a metal complex having an oxazole-based or thiazole-basedligand, such as bis[2-(2-benzoxazolyl)phenolato]zinc(II) (abbreviation:ZnPBO) or bis[2-(2-benzothiazolyl)phenolato]zinc(II) (abbreviation:ZnBTZ), can be used.

Specific examples of an oxadiazole derivative, a triazole derivative, abenzimidazole derivative, a quinoxaline derivative, a dibenzoquinoxalinederivative, and a phenanthroline derivative, which are organic compoundshaving a high electron-transport property, include2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (abbreviation:PBD), 1,3-bis[5-(p-tert-butylphenyl)-1,3,4-oxadiazol-2-yl]benzene(abbreviation: OXD-7),9-[4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl]-9H-carbazole (abbreviation:CO11), 3-(4-biphenylyl)-4-phenyl-5-(4-tert-butylphenyl)-1,2,4-triazole(abbreviation: TAZ),3-(4-tert-butylphenyl)-4-(4-ethylphenyl)-5-(4-biphenylyl)-1,2,4-triazole(abbreviation: p-EtTAZ),2-{4-[9,10-di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-1H-benzimidazole(abbreviation: ZADN),2,2′,2″-(1,3,5-benzenetriyl)tris(1-phenyl-1H-benzimidazole)(abbreviation: TPBI),2-[3-(dibenzothiophen-4-yl)phenyl]-1-phenyl-1H-benzimidazole(abbreviation: mDBTBIm-II), 4,4′-bis(5-methylbenzoxazol-2-yl)stilbene(abbreviation: BzOS), bathophenanthroline (abbreviation: Bphen),bathocuproine (abbreviation: BCP),2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline (abbreviation:NBphen), 2-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTPDBq-II),2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II),2-[3′-(9H-carbazol-9-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mCzBPDBq),2-[4-(3,6-diphenyl-9H-carbazol-9-yl)phenyl]dibenzo[f,h]quinoxaline(abbreviation: 2CzPDBq-III),7-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:7mDBTPDBq-II), and6-[3-(dibenzothiophen-4-yl)phenyl]dibenzo[f,h]quinoxaline (abbreviation:6mDBTPDBq-II).

Specific examples of a heterocyclic compound having a diazine skeleton,a heterocyclic compound having a triazine skeleton, and a heterocycliccompound having a pyridine skeleton, which are organic compounds havinga high electron-transport property, include4,6-bis[3-(phenanthren-9-yl)phenyl]pyrimidine (abbreviation:4,6mPnP2Pm), 4,6-bis[3-(4-dibenzothienyl)phenyl]pyrimidine(abbreviation: 4,6mDBTP2Pm-II),4,6-bis[3-(9H-carbazol-9-yl)phenyl]pyrimidine (abbreviation:4,6mCzP2Pm),2-{4-[3-(N-phenyl-9H-carbazol-3-yl)-9H-carbazol-9-yl]phenyl}-4,6-diphenyl-1,3,5-triazine(abbreviation: PCCzPTzn),9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-2,3′-bi-9H-carbazole(abbreviation: mPCCzPTzn-02),2-[3′-(9,9-dimethyl-9H-fluorene-2-yl)-1,1′-biphenyl-3-yl]-4,6-diphenyl-1,3,5-triazine(abbreviation: mFBPTzn),2-[(1,1′-biphenyl)-4-yl]-4-phenyl-6-[9,9′-spirobi(9H-fluoren)-2-yl]-1,3,5-triazine(abbreviation: BP-SFTzn),2-{3-[3-(benzo[b]naphtho[1,2-d]furan-8-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine(abbreviation: mBnfBPTzn),2-{3-[3-(benzo[b]naphtho[1,2-d]furan-6-yl)phenyl]phenyl}-4,6-diphenyl-1,3,5-triazine(abbreviation: mBnfBPTzn-02),3,5-bis(3-(9H-carbazol-9-yl)phenyl)pyridine (abbreviation: 35DCzPPy),and 1,3,5-tri[3-(3-pyridyl)phenyl]benzene (abbreviation: TmPyPB).

As an organic compound having a high electron-transport property, a highmolecular compound such as poly(2,5-pyridinediyl) (abbreviation: PPy),poly[(9,9-dihexylfluorene-2,7-diyl)-co-(pyridine-3,5-diyl)](abbreviation: PF-Py), orpoly[(9,9-dioctylfluorene-2,7-diyl)-co-(2,2′-bipyridine-6,6′-diyl)](abbreviation: PF-BPy) can also be used.

A TADF material has a small difference between the S₁ level (energylevel in a singlet excited state) and the T₁ level (energy level in atriplet excited state) and has a function of converting tripletexcitation energy into singlet excitation energy by reverse intersystemcrossing. Thus, a TADF material can upconvert triplet excitation energyinto singlet excitation energy (i.e., reverse intersystem crossing ispossible) using a small amount of thermal energy and efficientlygenerate a singlet excited state. In addition, the triplet excitationenergy can be converted into luminescence. Thermally activated delayedfluorescence is efficiently obtained under the condition where theenergy difference between the S₁ level and the T₁ level is greater thanor equal to 0 eV and less than or equal to 0.2 eV, preferably greaterthan or equal to 0 eV and less than or equal to 0.1 eV. Note that“delayed fluorescence” exhibited by the TADF material refers to lightemission having the same spectrum as normal fluorescence and anextremely long lifetime. The lifetime is 1×10⁻⁶ seconds or longer,preferably 1×10⁻³ seconds or longer.

An exciplex whose excited state is formed of two kinds of substances hasan extremely small difference between the S₁ level and the T₁ level andfunctions as a TADF material capable of converting triplet excitationenergy into singlet excitation energy.

A phosphorescent spectrum observed at low temperatures (e.g., 77 K to 10K) is used for an index of the T₁ level. When the level of energy with awavelength of the line obtained by extrapolating a tangent to thefluorescent spectrum at a tail on the short wavelength side is the S₁level and the level of energy with a wavelength of the line obtained byextrapolating a tangent to the phosphorescent spectrum at a tail on theshort wavelength side is the T₁ level, the difference between the S₁level and the T₁ level of the TADF material is preferably smaller thanor equal to 0.3 eV, further preferably smaller than or equal to 0.2 eV.

The TADF material may be used as a guest material or a host material.

Examples of the TADF material include fullerene, a derivative thereof,an acridine derivative such as proflavine, and eosin. Other examplesinclude a metal-containing porphyrin such as a porphyrin containingmagnesium (Mg), zinc (Zn), cadmium (Cd), tin (Sn), platinum (Pt), indium(In), or palladium (Pd). Examples of the metal-containing porphyrininclude a protoporphyrin-tin fluoride complex (abbreviation: SnF₂(ProtoIX)), a mesoporphyrin-tin fluoride complex (abbreviation: SnF₂(MesoIX)), a hematoporphyrin-tin fluoride complex (abbreviation: SnF₂(HematoIX)), a coproporphyrin tetramethyl ester-tin fluoride complex(abbreviation: SnF₂(Copro III-4Me)), an octaethylporphyrin-tin fluoridecomplex (abbreviation: SnF₂(OEP)), an etioporphyrin-tin fluoride complex(abbreviation: SnF₂(Etio I)), and an octaethylporphyrin-platinumchloride complex (abbreviation: PtCl₂OEP).

It is also possible to use a heterocyclic compound having a π-electronrich heteroaromatic ring and a π-electron deficient heteroaromatic ring,such as2-(biphenyl-4-yl)-4,6-bis(12-phenylindolo[2,3-a]carbazol-11-yl)-1,3,5-triazine(abbreviation: PIC-TRZ), PCCzPTzn,2-[4-(10H-phenoxazin-10-yl)phenyl]-4,6-diphenyl-1,3,5-triazine(abbreviation: PXZ-TRZ),3-[4-(5-phenyl-5,10-dihydrophenazin-10-yl)phenyl]-4,5-diphenyl-1,2,4-triazole(abbreviation: PPZ-3TPT),3-(9,9-dimethyl-9H-acridin-10-yl)-9H-xanthen-9-one (abbreviation:ACRXTN), bis[4-(9,9-dimethyl-9,10-dihydroacridine)phenyl]sulfone(abbreviation: DMAC-DPS),10-phenyl-10H,10′H-spiro[acridin-9,9′-anthracen]-10′-one (abbreviation:ACRSA), 4-(9′-phenyl-3,3′-bi-9H-carbazol-9-yl)benzofuro[3,2-d]pyrimidine(abbreviation: 4PCCzBfpm),4-[4-(9′-phenyl-3,3′-bi-9H-carbazol-9-yl)phenyl]benzofuro[3,2-d]pyrimidine(abbreviation: 4PCCzPBfpm), or9-[3-(4,6-diphenyl-1,3,5-triazin-2-yl)phenyl]-9′-phenyl-2,3′-bi-9H-carbazole(abbreviation: mPCCzPTzn-02). Such a heterocyclic compound is preferredbecause of having high electron-transport and hole-transport propertiesowing to a π-electron rich heteroaromatic ring and a π-electrondeficient heteroaromatic ring. Note that an aromatic ring to which anelectron-withdrawing group such as a cyano group is bonded may be usedinstead of the π-electron deficient heteroaromatic ring. Furthermore, aπ-electron deficient skeleton can be used instead of the π-electrondeficient heteroaromatic ring. Similarly, a π-electron rich skeleton canbe used instead of the π-electron rich heteroaromatic ring.

Among skeletons having the π-electron deficient heteroaromatic ring, apyridine skeleton, a diazine skeleton (a pyrimidine skeleton, a pyrazineskeleton, and a pyridazine skeleton), and a triazine skeleton arepreferred because of their high stability and reliability. Inparticular, a benzofuropyrimidine skeleton, a benzothienopyrimidineskeleton, a benzofuropyrazine skeleton, and a benzothienopyrazineskeleton are preferred because of their high electron-acceptingproperties and reliability.

Among skeletons having the π-electron rich heteroaromatic ring, anacridine skeleton, a phenoxazine skeleton, a phenothiazine skeleton, afuran skeleton, a thiophene skeleton, and a pyrrole skeleton have highstability and reliability; therefore, at least one of these skeletons ispreferably included. A dibenzofuran skeleton, a dibenzothiopheneskeleton, an indole skeleton, a carbazole skeleton, an indolocarbazoleskeleton, a bicarbazole skeleton, and a3-(9-phenyl-9H-carbazol-3-yl)-9H-carbazole skeleton are particularlypreferable.

Note that a substance in which a π-electron rich heteroaromatic ring isdirectly bonded to a π-electron deficient heteroaromatic ring isparticularly preferable because both the donor property of theπ-electron rich heteroaromatic ring and the acceptor property of theπ-electron deficient heteroaromatic ring are improved and the energydifference between the singlet excited state and the triplet excitedstate becomes small.

As a π-electron rich skeleton, an aromatic amine skeleton, a phenazineskeleton, or the like can be used. As a π-electron deficient skeleton, axanthene skeleton, a thioxanthene dioxide skeleton, an oxadiazoleskeleton, a triazole skeleton, an imidazole skeleton, an anthraquinoneskeleton, a boron-containing skeleton such as phenylborane orboranthrene, an aromatic ring or a heteroaromatic ring having a cyanogroup or a nitrile group, such as benzonitrile or cyanobenzene, acarbonyl skeleton such as benzophenone, a phosphine oxide skeleton, asulfone skeleton, or the like can be used.

Note that when a TADF material is used as the light-emitting substance,the TADF material can also be used in combination with another organiccompound. Specifically, the TADF material can be used in combinationwith the above-described host material (hole-transport material andelectron-transport material). In the case of using the TADF material,the S₁ level of the host material is preferably higher than that of theTADF material. In addition, the T₁ level of the host material ispreferably higher than that of the TADF material.

Alternatively, a TADF material may be used as a host material, and afluorescent material may be used as a guest material. When the TADFmaterial is used as the host material, triplet excitation energygenerated in the TADF material is converted into singlet excitationenergy by reverse intersystem crossing and transferred to thelight-emitting substance, whereby the emission efficiency of thelight-emitting device can be increased. Here, the TADF materialfunctions as an energy donor, and the light-emitting substance functionsas an energy acceptor. Therefore, the use of the TADF material as thehost material is highly effective in the case where a fluorescentmaterial is used as the guest material. In that case, it is preferablethat the S₁ level of the TADF material be higher than the S₁ level ofthe fluorescent material in order that high emission efficiency beachieved. Furthermore, the T₁ level of the TADF material is preferablyhigher than the S₁ level of the fluorescent material. Therefore, the T₁level of the TADF material is preferably higher than the T₁ level of thefluorescent material.

It is preferable to use a TADF material that emits light with awavelength that overlaps the wavelength of the absorption band on thelowest energy side of the fluorescent material, in which case theexcitation energy is smoothly transferred from the TADF material to thefluorescent material and light is emitted with high efficiency.

In addition, in order to efficiently generate singlet excitation energyfrom the triplet excitation energy by reverse intersystem crossing,carrier recombination preferably occurs in the TADF material. It is alsopreferable that the triplet excitation energy generated in the TADFmaterial not be transferred to the triplet excitation energy of thefluorescent material. For that reason, the fluorescent materialpreferably has a protective group around a luminophore (a skeleton thatcauses light emission) of the fluorescent material. As the protectivegroup, a substituent having no 1 bond and a saturated hydrocarbon arepreferably used. Specific examples include an alkyl group having 3 to 10carbon atoms, a substituted or unsubstituted cycloalkyl group having 3to 10 carbon atoms, and a trialkylsilyl group having 3 to 10 carbonatoms. It is further preferable that the fluorescent material have aplurality of protective groups. Since substituents having no 7 bond arepoor in carrier transport performance, the TADF material and theluminophore of the fluorescent material can be made away from each otherwith little influence on carrier transportation or carrierrecombination. Here, the luminophore refers to an atomic group(skeleton) that causes light emission in a fluorescent material. Theluminophore is preferably a skeleton having a π bond, further preferablyincludes an aromatic ring, and still further preferably includes acondensed aromatic ring or a condensed heteroaromatic ring. Examples ofthe condensed aromatic ring and the condensed heteroaromatic ringinclude a phenanthrene skeleton, a stilbene skeleton, an acridoneskeleton, a phenoxazine skeleton, and a phenothiazine skeleton.Specifically, a fluorescent material having any of a naphthaleneskeleton, an anthracene skeleton, a fluorene skeleton, a chryseneskeleton, a triphenylene skeleton, a tetracene skeleton, a pyreneskeleton, a perylene skeleton, a coumarin skeleton, a quinacridoneskeleton, and a naphthobisbenzofuran skeleton is preferred because ofits high fluorescence quantum yield.

<Electron-Transport Layer>

The electron-transport layer 124 transports electrons injected from thecathode 102, to the light-emitting layer 123.

The electron-transport layer 124 contains an electron-transport materialand a first substance.

The electron-transport material has an electron-transport propertyhigher than a hole-transport property.

The electron-transport material used for the electron-transport layer124 preferably has a highest occupied molecular orbital level (HOMOlevel) of −6.0 eV or higher.

The electron mobility of the electron-transport material used for theelectron-transport layer 124 is preferably higher than or equal to1×10⁻⁷ cm²/Vs and lower than or equal to 1×10⁻⁵ cm², further preferablyhigher than or equal to 1×10⁻⁷ cm²/Vs and lower than or equal to 5×10⁻⁵cm² in the case where the square root of the electric field strength[V/cm] is 600.

The electron mobility when the square root of the electric fieldstrength [V/cm] is 600 is preferably smaller in the electron-transportmaterial used for the electron-transport layer 124 than in the hostmaterial of the light-emitting layer 123. The amount of electronsinjected into the light-emitting layer 123 can be controlled by thereduction in the electron-transport property of the electron-transportlayer 124, whereby the light-emitting layer 123 can be prevented fromhaving excess electrons.

The electron-transport material used for the electron-transport layer124 preferably has an anthracene skeleton, and further preferably has ananthracene skeleton and a heterocyclic skeleton. The heterocyclicskeleton is preferably a nitrogen-containing five-membered ringskeleton. It is particularly preferred that the nitrogen-containingfive-membered ring skeleton include two heteroatoms in a ring, like apyrazol ring, an imidazole ring, an oxazole ring, or a thiazole ring.

In addition, some of the above-described electron-transport materialsthat can be used as the host material, or the above-described substancesgiven as materials that can be used as the host material in combinationwith the above fluorescent material can be used in theelectron-transport layer 124.

Examples of the electron-transport material used for theelectron-transport layer 124 include2-{4-[9,10-di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-H-benzimidazole(abbreviation: ZADN), 9-(1-naphthyl)-10-[4-(2-naphthyl)phenyl]anthracene(abbreviation: αN-βNPAnth),9-[4-(10-phenyl-9-anthracenyl)phenyl]-9H-carbazole (abbreviation: CzPA),and 7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA).

Other examples of the electron-transport material used for theelectron-transport layer 124 include the electron-transport materialsthat can be used in the above-described light-emitting layer and theorganic compounds (host materials) that can be used in combination withthe fluorescent material.

The first substance is a metal, a metallic salt, a metal oxide, or anorganometallic salt.

Examples of the metal include an alkali metal, an alkaline earth metal,and a rare earth metal. Specific examples include Li, Na, K, Rb, Cs, Mg,Ca, Sr, and Ba.

Examples of the metallic salt include halides of the above metals andcarbonates of the above metals. Specific examples include LiF, NaF, KF,RbF, CsF, MgF₂, CaF₂, SrF₂, BaF₂, LiCl, NaCl, KCl, RbCl, CsCl, MgCl₂,CaCl₂), SrCl₂, BaCl₂, Li₂CO₃, and Cs₂CO₃.

Examples of the metal oxide are oxides of the above metals. Specificexamples include Li₂O, Na₂O, Cs₂O, MgO, and CaO.

Examples of the organometallic salt are organometallic complexes.

The first substance is preferably an organometallic complex containingan alkali metal or an alkaline earth metal.

The first substance is preferably an organometallic complex including aligand containing nitrogen and oxygen, and an alkali metal or analkaline earth metal.

The first substance is preferably an organometallic complex including aquinolinol ligand, and an alkali metal or an alkaline earth metal.

Examples of the organometallic complex include 8-(quinolinolato)lithium(abbreviation: Liq), 8-hydroxyquinoline sodium salt (abbreviation: Naq),8-hydroxyquinoline potassium (abbreviation: Kq),bis(8-quinolinolato)magnesium (abbreviation: Mgq₂), andbis(8-quinolinolato)zinc(II) (abbreviation: Znq₂).

As the first substance, Liq is particularly preferable.

As illustrated in FIG. 18D, the electron-transport layer 124 may includethe electron-transport layer 124 a closer to the light-emitting layer123 and the electron-transport layer 124 b closer to the cathode 102.The electron-transport layer 124 a and the electron-transport layer 124b preferably have a different concentration ratio of theelectron-transport material to the first substance. For example, theconcentration of the first substance is preferably higher in theelectron-transport layer 124 a than in the electron-transport layer 124b.

<Electron-Injection Layer>

The electron-injection layer 125 increases the injection efficiency ofelectrons from the cathode 102. The difference between the work functionof the material of the cathode 102 and the LUMO level of the materialused for the electron-injection layer 125 is preferably small (within0.5 eV).

The electron-injection layer 125 can be formed using an alkali metal, analkaline earth metal, or a compound thereof, such as lithium, cesium,lithium fluoride (LiF), cesium fluoride (CsF), calcium fluoride (CaF₂),8-(quinolinolato)lithium (abbreviation: Liq),2-(2-pyridyl)phenolatolithium (abbreviation: LiPP),2-(2-pyridyl)-3-pyridinolato lithium (abbreviation: LiPPy),4-phenyl-2-(2-pyridyl)phenolato lithium (abbreviation: LiPPP), lithiumoxide (LiO_(x)), or cesium carbonate. A rare earth metal compound likeerbium fluoride (ErF₃) can also be used. Electride may also be used forthe electron-injection layer. An example of the electride includes asubstance in which electrons are added at high concentration to calciumoxide-aluminum oxide. Any of the above-described substances used for theelectron-transport layer can also be used.

A composite material containing an electron-transport material and adonor material (an electron-donating material) may be used for theelectron-injection layer. Such a composite material is excellent in anelectron-injection property and an electron-transport property becauseelectrons are generated in the organic compound by the electron donor.The organic compound here is preferably a material excellent intransporting the generated electrons; specifically, any of the aboveelectron-transport materials (e.g., the metal complexes and theheteroaromatic compounds) can be used, for example. As the electrondonor, a substance showing an electron-donating property with respect tothe organic compound is used. Specifically, an alkali metal, an alkalineearth metal, and a rare earth metal are preferable, and lithium, cesium,magnesium, calcium, erbium, ytterbium, and the like are given. Inaddition, an alkali metal oxide and an alkaline earth metal oxide arepreferable, and lithium oxide, calcium oxide, barium oxide, and the likeare given. Alternatively, a Lewis base such as magnesium oxide can beused. Further alternatively, an organic compound such astetrathiafulvalene (abbreviation: TTF) can be used.

<Charge Generation Layer>

The charge generation layer 104 has a function of injecting electronsinto the EL layer 103 a and injecting holes into the EL layer 103 b whenvoltage is applied between the anode 101 and the cathode 102.

The charge generation layer 104 may contain a hole-transport materialand an acceptor material or contain an electron-transport material and adonor material. Forming the charge generation layer 104 with such astructure can suppress an increase in the driving voltage that would becaused when the EL layers are stacked.

The hole-transport material, the acceptor material, theelectron-transport material, and the donor material can be any of thecorresponding materials described above.

For fabrication of the light-emitting device of this embodiment, avacuum process such as an evaporation method or a solution process suchas a spin coating method or an ink-jet method can be used. When anevaporation method is used, a physical vapor deposition method (PVDmethod) such as a sputtering method, an ion plating method, an ion beamevaporation method, a molecular beam evaporation method, or a vacuumevaporation method, a chemical vapor deposition method (CVD method), orthe like can be used. Specifically, the functional layers (thehole-injection layer, the hole-transport layers, the light-emittinglayer, the electron-transport layers, and the electron-injection layer)included in the EL layer can be formed by an evaporation method (e.g., avacuum evaporation method), a coating method (e.g., a dip coatingmethod, a die coating method, a bar coating method, a spin coatingmethod, or a spray coating method), a printing method (e.g., an ink-jetmethod, screen printing (stencil), offset printing (planography),flexography (relief printing), gravure printing, or micro-contactprinting), or the like.

The materials of the functional layers included in the light-emittingdevice are not limited to the above-described materials. For example, asthe materials of the functional layers, a high molecular compound (e.g.,an oligomer, a dendrimer, and a polymer), a middle molecular compound (acompound between a low molecular compound and a high molecular compoundwith a molecular weight of 400 to 4000), or an inorganic compound (e.g.,a quantum dot material) may be used. The quantum dot material may be acolloidal quantum dot material, an alloyed quantum dot material, acore-shell quantum dot material, a core quantum dot material, or thelike.

[Light Emission Model in Light-Emitting Device]

A light emission model of the light-emitting device of this embodimentwill be described.

Here, a light emission model of a light-emitting device is describedusing the hole-transport layer 122, the light-emitting layer 123, andthe electron-transport layer 124 in FIG. 18A. The light emission modelcan also apply to a light-emitting device having a structure other thanthat in FIG. 18A.

When the light-emitting layer 123 is in a state of having excesselectrons, a light-emitting region 123-1 is formed in a limited regionof the light-emitting layer 123, as illustrated in FIG. 19A. In otherwords, the width of the light-emitting region 123-1 in thelight-emitting layer 123 is small. Therefore, electrons (e) and holes(h+) are recombined intensively in the limited region of thelight-emitting layer 123, which accelerates degradation. In addition,the lifetime or emission efficiency may be reduced when electrons thathave not been recombined in the light-emitting layer 123 pass throughthe light-emitting layer 123.

Meanwhile, in the light-emitting device of one embodiment of the presentinvention, the width of the light-emitting region 123-1 in thelight-emitting layer 123 can be increased because of a lowelectron-transport property of the electron-transport layer 124 (FIGS.19B and 19C). Increasing the width of the light-emitting region 123-1enables an electron-hole recombination region in the light-emittinglayer 123 to be dispersed. Consequently, alight-emitting device withalong lifetime and high emission efficiency can be provided.

At the initial stage of driving of the light-emitting device of oneembodiment of the present invention, a recombination region may extendto the electron-transport layer 124, as illustrated in FIG. 19B. In FIG.19B, a recombination region in the electron-transport layer 124 isdenoted by a region 124-1. Specifically, in the light-emitting device ofone embodiment of the present invention, the light-emitting region 123-1(i.e., the recombination region) may be formed in the entirelight-emitting layer 123 and the recombination region may also be formedin the electron-transport layer 124, because a hole injection barrier issmall at the initial stage of driving and the electron-transportproperty of the electron-transport layer 124 is relatively low.

Since the HOMO level of the electron-transport material contained in theelectron-transport layer 124 is −6.0 eV or more, which is comparativelyhigh, some of holes may reach the electron-transport layer 124 andrecombination may be caused also in the electron-transport layer 124.Note that this phenomenon sometimes occurs when the difference in theHOMO level between the host material (or the assist material) containedin the light-emitting layer 123 and the electron-transport materialcontained in the electron-transport layer 124 is 0.2 eV or less.

As illustrated in FIG. 19C, the carrier balance changes as the drivingtime of the light-emitting device of one embodiment of the presentinvention increases, and thus recombination is less likely to occur inthe electron-transport layer 124. The recombination in theelectron-transport layer 124 is inhibited while the light-emittingregion 123-1 is formed in the entire light-emitting layer 123, wherebythe energy of recombined carriers can contribute effectively to lightemission. Accordingly, the luminance may increase compared to that atthe initial stage of driving. This luminance increase cancels out therapid luminance reduction at the initial stage of driving of thelight-emitting device, which is known as the initial decay. Thus, thelight-emitting device can have a long driving lifetime with a smallinitial decay. Note that in this specification and the like, thestructure of the above-described light-emitting device may be referredto as a Recombination-Site Tailoring Injection structure (ReSTIstructure).

Here, normalized luminance over time of light-emitting devices of thisembodiment and a comparative light-emitting device will be describedwith reference to FIG. 19D. In FIG. 19D, a thick solid line and a thickdashed-dotted line are decay curves of normalized luminance of thelight-emitting devices of this embodiment, and a solid dashed line is adecay curve of normalized luminance of the comparative light-emittingdevice.

As shown in FIG. 19D, the slope of the decay curve of normalizedluminance is different between the light-emitting devices of thisembodiment and the comparative light-emitting device. Specifically, aslope θ2 of the decay curve of the light-emitting device of thisembodiment is smaller than a slope θ1 of the decay curve of thecomparative light-emitting device.

As shown in FIG. 19D, the light-emitting device of one embodiment of thepresent invention may have a local maximum value (indicated by the thicksolid line) in the decay curve of luminance obtained in a driving testunder a condition with a fixed current density. In other words, thelight-emitting device of one embodiment of the present invention mayshow a behavior such that the luminance increases with time. Thisbehavior can cancel out rapid degradation at the initial stage ofdriving (i.e., initial decay). Note that the light-emitting device ofone embodiment of the present invention is not limited to the above; forexample, as indicated by the solid dashed-dotted line in FIG. 19D, theluminance does not have a local maximum value, that is, the slope of thedecay curve can be smaller without the luminance increase. Thus, thelight-emitting device having the structure showing the behavior can havea small initial decay and an extremely long driving lifetime.

Note that a differential value of the decay curve having the localmaximum value is 0 in a part. Therefore, a light-emitting device havinga decay curve whose differential value is 0 in a part can be referred toas a light-emitting device of one embodiment of the present invention.

In the light-emitting device of one embodiment of the present invention,the mix ratio (concentrations) of the electron-transport material andthe first substance in the electron-transport layer 124 preferablyvaries in the thickness direction. Specifically, the mix ratio(concentrations) of the electron-transport material and the metal,metallic salt, metal oxide, or organometallic complex preferably varies.

The concentration of the first substance in the electron-transport layer124 can be estimated from the amount of atoms and molecules detected bytime-of-flight secondary ion mass spectrometry (ToF-SIMS). In portionsthat contain the same two kinds of materials with different mix ratios,values measured by ToF-SIMS correspond to the amounts of targeted atomsor molecules. Therefore, comparing the detected amounts of theelectron-transport material and the organometallic complex allowsestimation of their mix ratio.

The amount of the first substance contained in the electron-transportlayer 124 is preferably smaller on the cathode 102 side than on theanode 101 side. In other words, the electron-transport layer 124 ispreferably formed so that the concentration of the first substanceincreases from the cathode 102 side to the anode 101 side. That is, inthe electron-transport layer 124, a portion with a low concentration ofthe electron-transport material is positioned closer to thelight-emitting layer 123 than a portion with a high concentration of theelectron-transport material is. In other words, in theelectron-transport layer 124, a portion with a high concentration of thefirst substance is positioned closer to the light-emitting layer 123than a portion with a low concentration of the first substance is.

In the electron-transport layer 124, the electron mobility of theportion with a high concentration of the electron-transport material(the portion with a low concentration of the first substance) ispreferably higher than or equal to 1×10⁻⁷ cm²/Vs and lower than or equalto 5×10⁻⁵ cm²/Vs when the square root of the electric field strength[V/cm] is 600.

For example, the amount (concentration) of the first substance in theelectron-transport layer 124 can be as shown in each of FIGS. 20A to20D. FIGS. 20A and 20B show the case where no clear boundary exists inthe electron-transport layer 124, and FIGS. 20C and 20D show the casewhere a clear boundary exists in the electron-transport layer 124.

In the case where no clear boundary exists in the electron-transportlayer 124, the concentrations of the electron-transport material and thefirst substance change continuously as shown in FIGS. 20A and 20B.Meanwhile, in the case where a clear boundary exists in theelectron-transport layer 124, the concentrations of theelectron-transport material and the first substance change in astep-like manner as shown in FIGS. 20C and 20D. The case where theconcentrations of the electron-transport material and the firstsubstance change in a step-like manner suggests that theelectron-transport layer 124 is formed of a plurality of layers. Forexample, FIG. 20C shows the case where the electron-transport layer 124has a two-layer structure, and FIG. 20D shows the case where theelectron-transport layer 124 has a three-layer structure. Note that inFIGS. 20C and 20D, a dashed line indicates a boundary region betweenlayers.

A change in carrier balance in the light-emitting device of oneembodiment of the present invention is probably caused by a change inelectron mobility of the electron-transport layer 124.

In the light-emitting device of one embodiment of the present invention,the concentration of the first substance varies in theelectron-transport layer 124. The electron-transport layer 124 includesa region with a high concentration of the first substance between aregion with a low concentration of the first substance and thelight-emitting layer 123. That is, the region with a low concentrationof the first substance is closer to the cathode 102 than the region witha high concentration of the first substance is.

The light-emitting device of one embodiment of the present inventionhaving the above structure has an extremely long lifetime. Inparticular, the time it takes for the luminance to decrease to 95% giventhat the initial luminance is 100% (the time can be referred to as LT95)can be extremely long.

This embodiment can be combined with the other embodiments asappropriate.

Embodiment 3

In this embodiment, the display unit of one embodiment of the presentinvention will be described with reference to FIGS. 21A and 21B andFIGS. 22A and 22B.

[Pixel Circuit Example 1]

In the display unit of one embodiment of the present invention, adisplay portion includes first pixel circuits including alight-receiving device and second pixel circuits including alight-emitting device. The first pixel circuits and the second pixelcircuits are arranged in a matrix.

FIG. 21A illustrates an example of the first pixel circuit including alight-receiving device. FIG. 21B illustrates an example of the secondpixel circuit including a light-emitting device.

A pixel circuit PIX1 illustrated in FIG. 21A includes thelight-receiving device PD, a transistor M1, a transistor M2, atransistor M3, a transistor M4, and a capacitor C1. Here, a photodiodeis used as an example of the light-receiving device PD.

A cathode of the light-receiving device PD is electrically connected toa wiring V1, and an anode of the light-receiving device PD iselectrically connected to one of a source and a drain of the transistorM1. A gate of the transistor M1 is electrically connected to a wiringTX, and the other of the source and the drain of the transistor M1 iselectrically connected to one electrode of the capacitor C1, one of asource and a drain of the transistor M2, and a gate of the transistorM3. A gate of the transistor M2 is electrically connected to a wiringRES, and the other of the source and the drain of the transistor M2 iselectrically connected to a wiring V2. One of a source and a drain ofthe transistor M3 is electrically connected to a wiring V3, and theother of the source and the drain of the transistor M3 is electricallyconnected to one of a source and a drain of the transistor M4. A gate ofthe transistor M4 is electrically connected to a wiring SE, and theother of the source and the drain of the transistor M4 is electricallyconnected to a wiring OUT1.

A constant potential is supplied to the wiring V1, the wiring V2, andthe wiring V3. When the light-receiving device PD is driven with areverse bias, the wiring V2 is supplied with a potential lower than thepotential of the wiring V1. The transistor M2 is controlled by a signalsupplied to the wiring RES and has a function of resetting the potentialof a node connected to the gate of the transistor M3 to a potentialsupplied to the wiring V2. The transistor M1 is controlled by a signalsupplied to the wiring TX and has a function of controlling the timingat which the potential of the node changes, in accordance with a currentflowing through the light-receiving device PD. The transistor M3functions as an amplifier transistor for outputting a signalcorresponding to the potential of the node. The transistor M4 iscontrolled by a signal supplied to the wiring SE and functions as aselection transistor for reading an output corresponding to thepotential of the node by an external circuit connected to the wiringOUT1.

A pixel circuit PIX2 illustrated in FIG. 21B includes a light-emittingdevice EL, a transistor M5, a transistor M6, a transistor M7, and acapacitor C2. Here, a light-emitting diode is used as an example of thelight-emitting device EL. In particular, an organic EL device ispreferably used as the light-emitting device EL.

A gate of the transistor M5 is electrically connected to a wiring VG,one of a source and a drain of the transistor M5 is electricallyconnected to a wiring VS, and the other of the source and the drain ofthe transistor M5 is electrically connected to one electrode of thecapacitor C2 and a gate of the transistor M6. One of a source and adrain of the transistor M6 is electrically connected to a wiring V4, andthe other is electrically connected to an anode of the light-emittingdevice EL and one of a source and a drain of the transistor M7. A gateof the transistor M7 is electrically connected to a wiring MS, and theother of the source and the drain of the transistor M7 is electricallyconnected to a wiring OUT2. A cathode of the light-emitting device EL iselectrically connected to a wiring V5.

A constant potential is supplied to the wiring V4 and the wiring V5. Theanode of the light-emitting device EL can be set to a high potential,and the cathode can be set to a lower potential than the anode. Thetransistor M5 is controlled by a signal supplied to the wiring VG andfunctions as a selection transistor for controlling a selection state ofthe pixel circuit PIX2. The transistor M6 functions as a drivingtransistor that controls a current flowing through the light-emittingdevice EL in accordance with a potential supplied to the gate of thetransistor M6. When the transistor M5 is on, a potential supplied to thewiring VS is supplied to the gate of the transistor M6, and theluminance of the light-emitting device EL can be controlled inaccordance with the potential. The transistor M7 is controlled by asignal supplied to the wiring MS and has a function of outputting apotential between the transistor M6 and the light-emitting device EL tothe outside through the wiring OUT2.

The wiring V1, to which the cathode of the light-receiving device PD iselectrically connected, and the wiring V5, to which the cathode of thelight-emitting device EL is electrically connected, can be provided inthe same layer and have the same potential.

Here, a transistor in which a metal oxide (an oxide semiconductor) isused in a semiconductor layer where a channel is formed is preferablyused as the transistors M1, M2, M3, and M4 included in the pixel circuitPIX1 and the transistors M5 M6, and M7 included in the pixel circuitPIX2.

A transistor using a metal oxide having a wider band gap and a lowercarrier density than silicon can achieve an extremely low off-statecurrent. Such a low off-state current enables retention of chargesaccumulated in a capacitor that is connected in series with thetransistor for a long time. Therefore, it is particularly preferable touse a transistor including an oxide semiconductor as the transistors M1,M2, and M5 each of which is connected in series with the capacitor C1 orthe capacitor C2. Moreover, the use of transistors including an oxidesemiconductor as the other transistors can reduce the manufacturingcost.

Alternatively, transistors using silicon as a semiconductor in which achannel is formed can be used as the transistors M1 to M7. Inparticular, the use of silicon with high crystallinity, such as singlecrystal silicon or polycrystalline silicon, is preferable because highfield-effect mobility is achieved and higher-speed operation ispossible.

Alternatively, a transistor including an oxide semiconductor may be usedas at least one of the transistors M1 to M7, and transistors includingsilicon may be used as the other transistors.

Although n-channel transistors are shown in FIGS. 21A and 21B, p-channeltransistors can alternatively be used.

The transistors included in the pixel circuit PIX1 and the transistorsincluded in the pixel circuit PIX2 are preferably formed side by sideover the same substrate. It is particularly preferable that thetransistors included in the pixel circuit PIX1 and the transistorsincluded in the pixel circuit PIX2 be periodically arranged in oneregion.

One or more layers including the transistor and/or the capacitor arepreferably provided to overlap with the light-receiving device PD or thelight-emitting device EL. Thus, the effective area of each pixel circuitcan be reduced, and a high-definition light-receiving portion or displayportion can be achieved.

[Pixel Circuit Example 2]

FIG. 22A is a block diagram of a pixel. The pixel illustrated in FIG.22A includes a memory (Memory) in addition to a switching transistor(Switching Tr), a driving transistor (Driving Tr), and a light-emittingdevice (OLED).

The memory is supplied with data Data_W. By supplying the data Data_W inaddition to display data Data to the pixel, the amount of currentflowing through the light-emitting device is increased, and the displayunit can have high luminance.

The display unit of one embodiment of the present invention capturesimages in such a manner that light emitted from the light-emittingdevice as a light source is used and light reflected by a subject isdetected by the light-receiving device. The light-emitting device usedas the light source is driven on the basis of the display data Data andthe data Data_W, whereby the light-emitting device can emit light withhigh luminance. Higher luminance of the light-emitting device results ina higher S/N ratio. Accordingly, the light detection sensitivity of thelight-emitting device can be increased.

FIG. 22B is a specific circuit diagram of the pixel circuit.

The pixel illustrated in FIG. 22B includes the transistor M1, thetransistor M2, the transistor M3, the transistor M4, a capacitor Cs, acapacitor Cw, and the light-emitting device EL.

One of the source and the drain of the transistor M1 is electricallyconnected to one electrode of the capacitor Cw. The other electrode ofthe capacitor Cw is electrically connected to one of the source and thedrain of the transistor M4. The one of the source and the drain of thetransistor M4 is electrically connected to the gate of the transistorM2. The gate of the transistor M2 is electrically connected to oneelectrode of the capacitor Cs. The other electrode of the capacitor Csis electrically connected to one of the source and the drain of thetransistor M2. The one of the source and the drain of the transistor M2is electrically connected to one of the source and the drain of thetransistor M3. The one of the source and the drain of the transistor M3is electrically connected to one electrode of the light-emitting deviceEL. The transistors illustrated in FIG. 22B each include a back gateelectrically connected to its gate; however, the connection of the backgate is not limited thereto. The transistor does not necessarily includethe back gate.

Here, a node to which the other electrode of the capacitor Cw, the oneof the source and the drain of the transistor M4, the gate of thetransistor M2, and the one electrode of the capacitor Cs are connectedis referred to as a node NM. Moreover, a node to which the otherelectrode of the capacitor Cs, the one of the source and the drain ofthe transistor M2, the one of the source and the drain of the transistorM3, and the one electrode of the light-emitting device EL are connectedis referred to as a node NA.

The gate of the transistor M1 is electrically connected to a wiring G1.The gate of the transistor M3 is electrically connected to the wiringG1. The gate of the transistor M4 is electrically connected to a wiringG2. The other of the source and the drain of the transistor M1 iselectrically connected to a wiring DATA. The other of the source and thedrain of the transistor M3 is electrically connected to a wiring V0. Theother of the source and the drain of the transistor M4 is electricallyconnected to a wiring DATA_W.

The other of the source and the drain of the transistor M2 iselectrically connected to a wiring ANODE (the high potential side). Theother electrode of the light-emitting device EL is electricallyconnected to a wiring CATHODE (the low potential side).

The wiring G1 and the wiring G2 can function as a signal line forcontrolling the operation of the corresponding transistor. The wiringDATA can function as a signal line for supplying an image signal to thepixel. The wiring DATA_W can function as a signal line for writing datato a memory circuit MEM. The wiring DATA_W can function as a signal linefor supplying a correction signal to the pixel. The wiring V0 functionsas a monitor line for obtaining the electrical characteristics of thetransistor M4. Supply of a specific potential from the wiring V0 to theother electrode of the capacitor Cs through the transistor M3 enablesstable writing of an image signal.

The memory circuit MEM is formed of the transistors M2, the transistorM4, and the capacitor Cw. The node NM is a storage node; when thetransistor M4 is turned on, a signal supplied to the wiring DATA_W canbe written to the node NM. The use of a transistor with an extremely lowoff-state current as the transistor M4 allows the potential of the nodeNM to be retained for a long time.

As the transistor M4, a transistor containing a metal oxide in itschannel formation region (hereinafter referred to as an OS transistor)can be used, for example. Thus, the off-state current of the transistorM4 can be extremely low, and the potential of the node NM can beretained for a long time. In this case, OS transistors are preferablyused as the other transistors included in the pixel. For the specificexample of the metal oxide, Embodiment 1 can be referred to.

An OS transistor has a large energy gap and thus has an extremely lowoff-state current. Unlike in a transistor in which Si is included in thechannel formation region (hereinafter referred to as a Si transistor),impact ionization, avalanche breakdown, short-channel effects, and thelike do not occur in an OS transistor; accordingly, a highly reliablecircuit can be configured.

Furthermore, a Si transistor may be used as the transistor M4. In thiscase, Si transistors are preferably used as the other transistorsincluded in the pixel.

Examples of the Si transistor include a transistor containing amorphoussilicon, a transistor containing crystalline silicon (typically,low-temperature polysilicon), and a transistor containing single crystalsilicon.

Alternatively, one pixel may include both an OS transistor and a Sitransistor.

In the pixel, a signal written to the node NM is capacitively coupled toan image signal supplied from the wiring DATA, and the resulting datacan be output to the node NA. Note that the transistor M1 can have afunction of selecting a pixel.

In other words, when an intended correction signal is stored in the nodeNM in advance, the correction signal can be added to the supplied imagesignal. Note that the correction signal is sometimes attenuated by acomponent on the transmission path; hence, the signal is preferablyproduced in consideration of the attenuation.

When the light-emitting device is made to emit light with the use of theimage signal and the correction signal, the amount of current flowingthrough the light-emitting device can be increased, and high luminancecan be achieved. A voltage higher than the output voltage of a sourcedriver can be applied as the gate voltage of the driving transistor, sothat power consumption of the source driver can be reduced. Sincehigh-luminance light can be used for a light source, the sensitivity ofthe sensor can be increased.

This embodiment can be combined with the other embodiments asappropriate.

Embodiment 4

In this embodiment, electronic devices of one embodiment of the presentinvention will be described with reference to FIGS. 23A and 23B, FIGS.24A to 24D, and FIGS. 25A to 25F.

An electronic device of this embodiment includes the display unit of oneembodiment of the present invention. For example, the display unit ofone embodiment of the present invention can be used in a display portionof the electronic device. The display unit of one embodiment of thepresent invention has a function of sensing light, and thus can performbiological authentication with the display portion or detect a touch ora near touch on the display portion. That is, the light-receiving deviceincluded in the display unit of one embodiment of the present inventioncan function as a touch sensor or part of a touch panel, therebyimproving the functionality and convenience of the electronic device,for example.

Examples of the electronic devices include a digital camera, a digitalvideo camera, a digital photo frame, a mobile phone, a portable gameconsole, a portable information terminal, and an audio reproducingdevice, in addition to electronic devices with a relatively largescreen, such as a television device, a desktop or laptop personalcomputer, a monitor of a computer or the like, digital signage, and alarge game machine such as a pachinko machine.

The electronic device in this embodiment may include a sensor (a sensorhaving a function of measuring force, displacement, position, speed,acceleration, angular velocity, rotational frequency, distance, light,liquid, magnetism, temperature, a chemical substance, sound, time,hardness, electric field, current, voltage, electric power, radiation,flow rate, humidity, gradient, oscillation, a smell, or infrared rays).

The electronic device in this embodiment can have a variety offunctions. For example, the electronic device can have a function ofdisplaying a variety of data (a still image, a moving image, a textimage, and the like) on the display portion, a touch panel function, afunction of displaying a calendar, date, time, and the like, a functionof executing a variety of software (programs), a wireless communicationfunction, and a function of reading out a program or data stored in arecording medium.

An electronic device 6500 in FIG. 23A is a portable information terminalthat can be used as a smartphone.

The electronic device 6500 includes a housing 6501, a display portion6502, a power button 6503, buttons 6504, a speaker 6505, a microphone6506, a camera 6507, a light source 6508, and the like. The displayportion 6502 has a touch panel function.

The display unit of one embodiment of the present invention can be usedin the display portion 6502.

FIG. 23B is a schematic cross-sectional view including an end portion ofthe housing 6501 on the microphone 6506 side.

A protective component 6510 having a light-transmitting property isprovided on the display surface side of the housing 6501. A displaypanel 6511, an optical component 6512, a touch sensor panel 6513, aprinted circuit board 6517, a battery 6518, and the like are provided ina space surrounded by the housing 6501 and the protective component6510.

The display panel 6511, the optical component 6512, and the touch sensorpanel 6513 are fixed to the protective component 6510 with an adhesivelayer (not illustrated).

Part of the display panel 6511 is folded back in a region outside thedisplay portion 6502, and an FPC 6515 is connected to the part that isfolded back. An IC 6516 is mounted on the FPC 6515. The FPC 6515 isconnected to a terminal provided on the printed circuit board 6517.

A flexible display of one embodiment of the present invention can beused as the display panel 6511. Thus, an extremely lightweightelectronic device can be provided. Since the display panel 6511 isextremely thin, the battery 6518 with high capacity can be mounted withthe thickness of the electronic device controlled. An electronic devicewith a narrow frame can be obtained when part of the display panel 6511is folded back so that the portion connected to the FPC 6515 ispositioned on the rear side of a pixel portion.

FIG. 24A illustrates an example of a television device. In a televisiondevice 7100, a display portion 7000 is incorporated in a housing 7101.Here, a structure in which the housing 7101 is supported by a stand 7103is illustrated.

The display unit of one embodiment of the present invention can be usedin the display portion 7000.

The television device 7100 illustrated in FIG. 24A can be operated withan operation switch provided in the housing 7101 or a separate remotecontroller 7111. Alternatively, the display portion 7000 may include atouch sensor, and the television device 7100 may be operated by touch onthe display portion 7000 with a finger or the like. The remotecontroller 7111 may be provided with a display portion for displayinginformation output from the remote controller 7111. With a touch panelor operation keys provided in the remote controller 7111, channels andvolume can be controlled, and videos displayed on the display portion7000 can be controlled.

Note that the television device 7100 is provided with a receiver, amodem, and the like. A general television broadcast can be received withthe receiver. When the television device is connected to a communicationnetwork with or without wires via the modem, one-way (from a transmitterto a receiver) or two-way (between a transmitter and a receiver orbetween receivers, for example) data communication can be performed.

FIG. 24B illustrates an example of a laptop personal computer. A laptoppersonal computer 7200 includes a housing 7211, a keyboard 7212, apointing device 7213, an external connection port 7214, and the like.The display portion 7000 is incorporated in the housing 7211.

The display unit of one embodiment of the present invention can be usedin the display portion 7000.

FIGS. 24C and 24D illustrate examples of digital signage.

Digital signage 7300 illustrated in FIG. 24C includes a housing 7301,the display portion 7000, a speaker 7303, and the like. Furthermore, thedigital signage can include an LED lamp, operation keys (including apower switch or an operation switch), a connection terminal, a varietyof sensors, a microphone, and the like.

FIG. 24D illustrates digital signage 7400 mounted on a cylindricalpillar 7401. The digital signage 7400 includes the display portion 7000provided along a curved surface of the pillar 7401.

The display unit of one embodiment of the present invention can be usedin the display portion 7000 illustrated in each of FIGS. 24C and 24D.

A larger area of the display portion 7000 can increase the amount ofdata that can be provided at a time. The larger display portion 7000attracts more attention, so that the effectiveness of the advertisementcan be increased, for example.

It is preferable to use a touch panel in the display portion 7000because a device with such a structure does not just display still ormoving images on the display portion 7000 but can be operated by usersintuitively. Moreover, for an application for providing information suchas route information or traffic information, usability can be enhancedby intuitive operation.

It is preferable that the digital signage 7300 or the digital signage7400 work with an information terminal 7311 or an information terminal7411 such as a user's smartphone through wireless communication, asillustrated in FIGS. 24C and 24D. For example, information of anadvertisement displayed on the display portion 7000 can be displayed ona screen of the information terminal 7311 or the information terminal7411. By operation of the information terminal 7311 or the informationterminal 7411, display on the display portion 7000 can be switched.

It is possible to make the digital signage 7300 or the digital signage7400 execute a game with the use of the screen of the informationterminal 7311 or the information terminal 7411 as an operation means(controller). Thus, an unspecified number of people can join in andenjoy the game concurrently.

Electronic devices illustrated in FIGS. 25A to 25F include a housing9000, a display portion 9001, a speaker 9003, an operation key 9005(including a power switch or an operation switch), a connection terminal9006, a sensor 9007 (a sensor having a function of measuring force,displacement, position, speed, acceleration, angular velocity,rotational frequency, distance, light, liquid, magnetism, temperature, achemical substance, sound, time, hardness, electric field, current,voltage, electric power, radiation, flow rate, humidity, gradient,oscillation, a smell, or infrared rays), a microphone 9008, and thelike.

The electronic devices illustrated in FIGS. 25A to 25F have a variety offunctions. For example, the electronic devices can have a function ofdisplaying a variety of data (a still image, a moving image, a textimage, and the like) on the display portion, a touch panel function, afunction of displaying a calendar, date, time, and the like, a functionof controlling processing with the use of a variety of software(programs), a wireless communication function, and a function of readingout and processing a program or data stored in a recording medium. Notethat the functions of the electronic devices are not limited thereto,and the electronic devices can have a variety of functions. Theelectronic devices may include a plurality of display portions. Theelectronic devices may include a camera or the like and have a functionof taking a still image or a moving image and storing the taken image ina recording medium (an external recording medium or a recording mediumincorporated in the camera), a function of displaying the taken image onthe display portion, or the like.

The electronic devices illustrated in FIGS. 25A to 25F are described indetail below.

FIG. 25A is a perspective view illustrating a portable informationterminal 9101. The portable information terminal 9101 can be used as asmartphone, for example. Note that the portable information terminal9101 may be provided with the speaker 9003, the connection terminal9006, the sensor 9007, or the like. The portable information terminal9101 can display text and image information on its plurality ofsurfaces. FIG. 25A shows an example where three icons 9050 aredisplayed. Information 9051 indicated by dashed rectangles can bedisplayed on another surface of the display portion 9001. Examples ofthe information 9051 include notification of reception of an e-mail, anSNS message, or an incoming call, the title and sender of an e-mail, anSNS message, or the like, the date, the time, remaining battery, and thereception strength of an antenna. Alternatively, the icon 9050 or thelike may be displayed at the position where the information 9051 isdisplayed.

FIG. 25B is a perspective view illustrating a portable informationterminal 9102. The portable information terminal 9102 has a function ofdisplaying information on three or more surfaces of the display portion9001. Here, an example in which information 9052, information 9053, andinformation 9054 are displayed on different surfaces is shown. Forexample, the user can check the information 9053 displayed at a positionthat can be observed from above the portable information terminal 9102,with the portable information terminal 9102 put in a breast pocket ofhis/her clothes. The user can see the display without taking out theportable information terminal 9102 from the pocket and decide whether toanswer the call, for example.

FIG. 25C is a perspective view illustrating a watch-type portableinformation terminal 9200. The portable information terminal 9200 can beused as a smart watch, for example. The display surface of the displayportion 9001 is curved, and display can be performed along the curveddisplay surface. Furthermore, for example, mutual communication betweenthe portable information terminal 9200 and a headset capable of wirelesscommunication can be performed, and thus hands-free calling is possible.With the connection terminal 9006, the portable information terminal9200 can perform mutual data transmission with another informationterminal and charging. Note that the charging operation may be performedby wireless power feeding.

FIGS. 25D, 25E, and 25F are perspective views of a foldable portableinformation terminal 9201 that is opened, that is shifted from theopened state to the folded state or from the folded state to the openedstate, and that is folded, respectively. The portable informationterminal 9201 is highly portable in the folded state and is highlybrowsable in the opened state because of a seamless large displayregion. The display portion 9001 of the portable information terminal9201 is supported by three housings 9000 joined by hinges 9055. Forexample, the display portion 9001 can be folded with a radius ofcurvature of greater than or equal to 0.1 mm and less than or equal to150 mm.

This embodiment can be combined with the other embodiments asappropriate.

Reference Example

In this reference example, methods for calculating the HOMO level, theLUMO level, and the electron mobility of an organic compound in thedisplay unit of one embodiment of the present invention will bedescribed.

The HOMO level and the LUMO level can be calculated through a cyclicvoltammetry (CV) measurement.

In this reference example, an electrochemical analyzer (ALS model 600Aor 600C, produced by BAS Inc.) was used as the measurement apparatus. Asolution for the CV measurement was prepared in the following manner:tetra-n-butylammonium perchlorate (n-Bu₄NClO₄, produced by TokyoChemical Industry Co., Ltd., catalog No. T0836) as a supportingelectrolyte was dissolved in dehydrated dimethylformamide (DMF, producedby Sigma-Aldrich Co. LLC., 99.8%, catalog No. 22705-6) as a solvent at aconcentration of 100 mmol/L, and the object to be measured was dissolvedtherein at a concentration of 2 mmol/L. A platinum electrode (PTEplatinum electrode manufactured by BAS Inc.) was used as a workingelectrode, another platinum electrode (Pt counter electrode for VC-3 (5cm), manufactured by BAS Inc.) was used as an auxiliary electrode, andan Ag/Ag⁺ electrode (RE7 reference electrode for nonaqueous solvent,manufactured by BAS Inc.) was used as a reference electrode. Themeasurement was conducted at room temperature (20° C. to 25° C.). Thescan speed in the CV measurement was set to 0.1 V/sec, and an oxidationpotential Ea [V] and a reduction potential Ec [V] with respect to thereference electrode were measured. The potential Ea was an intermediatepotential of an oxidation-reduction wave, and the potential Ec was anintermediate potential of a reduction-oxidation wave. Here, thepotential energy of the reference electrode used in this referenceexample with respect to the vacuum level is known to be −4.94 [eV]; theHOMO level and the LUMO level can be calculated by the followingformulae: HOMO level [eV]=−4.94−Ea and LUMO level [eV]=−4.94−Ec.

The electron mobility can be measured by an impedance spectroscopy (IS)method.

As a method of measuring the carrier mobility of an EL material, atime-of-flight (TOF) method, a method using I-V characteristics of aspace-charge-limited current (SCLC), or the like has been known for along time. The TOF method needs a sample with a much larger thicknessthan that of an actual organic EL device. The SCLC method has adisadvantage in that electric field strength dependence of carriermobility cannot be obtained, for example. Since an organic film requiredfor the measurement employing the IS method is thin (approximatelyseveral hundreds of nanometers), the organic film can be formed of arelatively small amount of EL materials, whereby the mobility can bemeasured with a thickness close to the thickness of a film in an actualorganic EL device. In this method, the electric field strengthdependence of the carrier mobility can also be measured.

In the IS method, a micro sinusoidal voltage signal (V=V₀[exp(cωt)]) isapplied to an EL device, and the impedance (Z=V/I) of the EL device isobtained from a phase difference between the current amplitude of aresponse current signal (I=I₀exp[j(ωt+ϕ)]) and the input signal. Whenthe micro sinusoidal voltage signal that is changed from a highfrequency voltage to a low frequency voltage is applied to the ELdevice, components having various relaxation times that contribute tothe impedance can be separated and measured.

Here, admittance Y (=1/Z), which is the reciprocal of the impedance, canbe represented by conductance G and susceptance B as shown in thefollowing formula (1).

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 1} \right\rbrack\mspace{625mu}} & \; \\{Y = {\frac{1}{Z} = {G + {jB}}}} & (1)\end{matrix}$

In addition, by a single injection model, calculation of the followingformulae (2) and (3) can be performed. Here, g in the formula (4) isdifferential conductance. In the formulae, C represents capacitance, θrepresents a transit angle (ωT), ω represents angular frequency, and Trepresents transit time. For the analysis, the current equation, thePoisson equation and the current continuity equation are used, and adiffusion current and a trap state are ignored.

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 2} \right\rbrack\mspace{625mu}} & \; \\{G = {\frac{g\theta^{3}}{6}\frac{\theta - {\sin\;\theta}}{\left( {\theta - {\sin\;\theta}} \right)^{2} + \left( {\frac{\theta^{2}}{2} + {\cos\;\theta} - 1} \right)^{2}}}} & (2) \\{B = {{\omega\; C} = {\frac{g\theta^{3}}{6}\frac{\frac{\theta^{2}}{2} + {\cos\;\theta} - 1}{\left( {\theta - {\sin\theta}} \right)^{2} + \left( {\frac{\theta^{2}}{2} + {\cos\;\theta} - 1} \right)^{2}}}}} & (3) \\{g = {\frac{9}{4}ɛ\mu\frac{V_{0}}{d^{3}}}} & (4)\end{matrix}$

A method of calculating mobility from the frequency characteristics ofcapacitance is a −ΔB method. A method of calculating mobility from thefrequency characteristics of conductance is a ωΔG method.

In practice, an electron-only device is first fabricated using thematerial whose electron mobility is intended to be calculated. Theelectron-only device is a device designed such that only electrons flowtherein as carriers. In this specification, a method of calculatingmobility from the frequency characteristics of capacitance (the −ΔBmethod) is described.

FIG. 26 illustrates a structure of an electron-only device fabricatedfor the measurement, and Table 1 shows its specific components. Theelectron-only device fabricated in this reference example includes afirst layer 910, a second layer 911, and a third layer 912 between afirst electrode 901 (anode) and a second electrode 902 (cathode). Thematerial whose electron mobility is intended to be calculated is used asa material for the second layer 911. In this reference example, theelectron mobility of a film formed by co-evaporation of2-{4-[9,10-di(naphthalen-2-yl)-2-anthryl]phenyl}-1-phenyl-H-benzimidazole(abbreviation: ZADN) and 8-(quinolinolato)lithium (abbreviation: Liq) ina weight ratio of 1:1 was measured. In this reference example, theelectron mobility was also measured for7-[4-(10-phenyl-9-anthryl)phenyl]-7H-dibenzo[c,g]carbazole(abbreviation: cgDBCzPA) and2-[3′-(dibenzothiophen-4-yl)biphenyl-3-yl]dibenzo[f,h]quinoxaline(abbreviation: 2mDBTBPDBq-II).

TABLE 1 Second First Second Third electrode First electrode (anode)layer layer layer (cathode) 100 nm 50 nm 100 nm 1 nm 200 nm 1 nm 100 nmAPC ITSO Al Liq ZADN:Liq Liq Al (0.5:0.5)

FIG. 27 shows the current density-voltage characteristics of theelectron-only device using the film formed by co-evaporation of ZADN andLiq as the second layer 911.

The impedance was measured under the conditions where the AC voltage was70 mV and the frequency was from 1 Hz to 3 MHz with a DC voltage in therange of 5.0 V to 9.0 V applied. Here, capacitance is calculated fromthe admittance (the above formula (1)), which is the reciprocal of theobtained impedance. FIG. 28 shows the frequency characteristics of thecalculated capacitance C when the applied voltage was 7.0 V.

The frequency characteristics of the capacitance C are obtained from aphase difference in current, which is caused because a space chargegenerated by carriers injected by the micro voltage signal cannotcompletely follow the micro AC voltage. The transit time of the carriersin the film is defined by time T it takes for the injected carriers toreach the counter electrode, and is represented by the following formula(5).

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 3} \right\rbrack\mspace{625mu}} & \; \\{T = {\frac{4}{3}\frac{L^{2}}{\mu\; V_{0}}}} & (5)\end{matrix}$

A negative susceptance change (−ΔB) corresponds to a value (−ωΔC) thatis obtained by multiplying a capacitance change −ΔC by an angularfrequency ω. The formula (3) shows that there is a relation between peakfrequency on the lowest frequency side f′_(max) (=ω_(max)/2π) and thetransit time T as represented in the following formula (6).

$\begin{matrix}{\left\lbrack {{Formula}\mspace{14mu} 4} \right\rbrack\mspace{625mu}} & \; \\{T = \frac{4.5}{2\pi\; f_{\max}^{\prime}}} & (6)\end{matrix}$

FIG. 29 shows the frequency characteristics of −ΔB calculated from theabove measurement (i.e., −ΔB when the DC voltage was 7.0 V). The peakfrequency on the lowest frequency side f′_(max) is indicated by an arrowin FIG. 29 .

The transit time T is obtained from f′_(max) obtained from the abovemeasurement and analysis (the formula (6)); thus, in this example, theelectron mobility at a DC voltage of 7.0 V can be obtained from theabove formula (5). Through the same measurement with the DC voltage inthe range of 5.0 V to 9.0 V, the electron mobility at each voltage(electric field strength) can be calculated, so that the electric fieldstrength dependence of the mobility can also be measured.

FIG. 30 shows the electric field strength dependence of the electronmobility of the organic compounds, which was eventually obtained by theabove calculation method. Table 2 shows the electron mobility read fromFIG. 30 in the case where the square root of the electric field strength[V/cm] was 600 [V/cm]^(1/2). In FIG. 30 , a square represents the resultof cgDBCzPA, a triangle represents the result of 2mDBTBPDBq-II, and arhombus represents the result of the film formed by co-evaporation ofZADN and Liq.

TABLE 2 Electron mobility (cm²/Vs) cgDBCzPA 7.7 × 10⁻⁵ 2mDBTBPDBq-II 2.2× 10⁻⁵ ZADN:Liq 3.5 × 10⁻⁶ (1:1)

The electron mobility can be calculated in the above manner. Note thatthe following reference can be referred to for the details of themeasurement method: T. Okachi et al., Japanese Journal of AppliedPhysics, Vol. 47, No. 12, pp. 8965-8972, 2008.

This application is based on Japanese Patent Application Serial No.2019-126332 filed with Japan Patent Office on Jul. 5, 2019, the entirecontents of which are hereby incorporated by reference.

What is claimed is:
 1. A display unit comprising: a substrate; alight-receiving device over the substrate, the light-receiving devicecomprising: a first pixel electrode; an active layer comprising a firstorganic compound; and a common electrode over the first pixel electrode;a light-emitting device over the substrate, the light-emitting devicecomprising: a second pixel electrode; a hole-injection layer over thesecond pixel electrode, the hole-injection layer comprising a firstcompound and a second compound; a light-emitting layer over the secondpixel electrode, the light-emitting layer comprising a second organiccompound; an electron-transport layer over the second pixel electrode,the electron-transport layer comprising an electron-transport material;and the common electrode over the second pixel electrode, thehole-injection layer, the light-emitting layer and theelectron-transport layer; a resin layer between the substrate and thecommon electrode; and a light-blocking layer between the resin layer andthe common electrode, wherein the resin layer comprises an openingoverlapping with the light-receiving device, wherein the resin layer andthe light-emitting device overlap each other, wherein the commonelectrode, the active layer and the first pixel electrode overlap oneanother, wherein the common electrode, the light-emitting layer and thesecond pixel electrode overlap one another, wherein the hole-injectionlayer is in contact with one of the second pixel electrode and thecommon electrode, wherein the second organic compound is different fromthe first organic compound, wherein the first compound has a property ofaccepting electrons from the second compound, wherein the secondcompound has a Highest Occupied Molecular Orbital (HOMO) level higherthan or equal to −5.7 eV and lower than or equal to −5.4 eV, wherein theelectron-transport material has a Highest Occupied Molecular Orbital(HOMO) level higher than or equal to −6.0 eV, and wherein theelectron-transport material has an electron mobility higher than orequal to 1×10⁻⁷ cm²/Vs and lower than or equal to 5×10⁻⁵ cm²/Vs when asquare root of electric field strength is 600 (V/cm)^(1/2).
 2. Thedisplay unit according to claim 1, wherein the one of the second pixelelectrode and the common electrode is an anode.
 3. The display unitaccording to claim 1, wherein the light-receiving device furthercomprises the hole-injection layer over the first pixel electrode,wherein the hole-injection layer and the active layer overlap eachother, and wherein the hole-injection layer and the light-emitting layeroverlap each other.
 4. The display unit according to claim 1, whereinthe light-receiving device further comprises the electron-transportlayer over the first pixel electrode, and wherein the electron-transportlayer comprises a portion overlapping with the active layer and aportion overlapping with the light-emitting layer.
 5. The display unitaccording to claim 1, wherein the light-receiving device and thelight-emitting device further comprise a common layer, wherein thecommon layer is positioned over the first pixel electrode and the secondpixel electrode, and wherein the common layer comprises a portionoverlapping with the active layer and a portion overlapping with thelight-emitting layer.
 6. The display unit according to claim 1, whereinthe light-emitting device emits blue light.
 7. The display unitaccording to claim 1, wherein the light-emitting device is a fluorescentdevice.
 8. The display unit according to claim 1, wherein thelight-blocking layer covers at least part of the opening and at leastpart of a side surface of the resin layer exposed in the opening.
 9. Thedisplay unit according to claim 1, further comprising: a substrate; aresin layer between the substrate and the common electrode; and alight-blocking layer between the resin layer and the common electrode,wherein the resin layer and the light-blocking layer are positionedbetween the common electrode and the substrate, wherein the resin layerhas an island shape, wherein the resin layer and the light-emittingdevice overlap each other, and wherein at least part of incident lightpassing through the substrate is configured to enter the light-receivingdevice without passing through the resin layer.
 10. The display unitaccording to claim 9, wherein the light-blocking layer covers at leastpart of a side surface of the resin layer.
 11. The display unitaccording to claim 1, further comprising an adhesive layer between thesubstrate and the common electrode, wherein each of the resin layer andthe light-blocking layer is positioned between the substrate and theadhesive layer, wherein a first portion of the adhesive layer and thelight-receiving device overlap each other, wherein a second portion ofthe adhesive layer and the light-emitting device overlap each other, andwherein the first portion of the adhesive layer is thicker than thesecond portion of the adhesive layer.
 12. A display module comprising:the display unit according to claim 1; and one of a connector and anintegrated circuit.
 13. An electronic device comprising: the displaymodule according to claim 12; and at least one of an antenna, a battery,a housing, a camera, a speaker, a microphone and an operation button.14. A display unit comprising: a light-receiving device comprising: afirst pixel electrode; an active layer comprising a first organiccompound; and a common electrode over the first pixel electrode; and alight-emitting device comprising: a second pixel electrode; alight-emitting layer over the second pixel electrode, the light-emittinglayer comprising a second organic compound; an electron-transport layerover the second pixel electrode; and the common electrode over thesecond pixel electrode, the light-emitting layer and theelectron-transport layer, wherein the second organic compound isdifferent from the first organic compound, wherein the common electrode,the active layer and the first pixel electrode overlap one another,wherein the common electrode, the light-emitting layer and the secondpixel electrode overlap one another, wherein the electron-transportlayer comprises a first region and a second region, wherein each of thefirst region and the second region comprises an electron-transportmaterial and a first substance, wherein the first region has a differentconcentration of the first substance from the second region, and whereinthe first substance is one of a metal, a metallic salt, a metal oxideand an organometallic complex.
 15. The display unit according to claim14, wherein the first region is positioned between the light-emittinglayer and the second region, and wherein the first region has a higherconcentration of the first substance than the second region.
 16. Thedisplay unit according to claim 14, wherein the electron-transportmaterial has a Highest Occupied Molecular Orbital (HOMO) level higherthan or equal to −6.0 eV, and wherein the electron-transport materialhas an electron mobility higher than or equal to 1×10⁻⁷ cm²/Vs and lowerthan or equal to 5×10⁻⁵ cm²/Vs when a square root of electric fieldstrength is 600 (V/cm)^(1/2).
 17. The display unit according to claim14, wherein the light-emitting device further comprises a hole-injectionlayer, wherein the hole-injection layer is in contact with one of thesecond pixel electrode and the common electrode, wherein the one of thesecond pixel electrode and the common electrode is an anode, wherein thehole-injection layer comprises a first compound and a second compound,wherein the first compound has a property of accepting electrons fromthe second compound, and wherein the second compound has a HighestOccupied Molecular Orbital (HOMO) level higher than or equal to −5.7 eVand lower than or equal to −5.4 eV.
 18. The display unit according toclaim 14, wherein the light-receiving device further comprises theelectron-transport layer over the first pixel electrode, wherein theelectron-transport layer and the active layer overlap each other, andwherein the electron-transport layer and the light-emitting layeroverlap each other.
 19. The display unit according to claim 14, whereinthe light-receiving device and the light-emitting device furthercomprise a common layer, wherein the common layer is positioned over thefirst pixel electrode and the second pixel electrode, wherein a firstportion of the common layer and the active layer overlap each other, andwherein a second portion of the common layer and the light-emittinglayer overlap each other.
 20. The display unit according to claim 14,wherein the light-emitting device emits blue light.
 21. The display unitaccording to claim 14, wherein the light-emitting device is afluorescent device.
 22. The display unit according to claim 14, furthercomprising: a substrate; a resin layer between the substrate and thecommon electrode; and a light-blocking layer between the resin layer andthe common electrode, wherein the resin layer comprises an openingoverlapping with the light-receiving device, and wherein the resin layerand the light-emitting device overlap each other.
 23. A display modulecomprising: the display unit according to claim 14; and one of aconnector and an integrated circuit.
 24. An electronic devicecomprising: the display module according to claim 23; and at least oneof an antenna, a battery, a housing, a camera, a speaker, a microphoneand an operation button.